Pollution: ICSE Class 9 Geography solution

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Get notes, summary, questions and answers, MCQs, extras, and PDFs of Chapter 16 “Pollution” which is part of ICSE Class 9 Geography (Morning Star/Total) textbook/workbook answers. However, the notes should only be treated as references and changes should be made according to the needs of the students.

Summary

Pollution happens when our environment’s natural quality changes badly. Chemical, physical, or biological factors cause these changes. Environmental pollution is an unfavorable alteration of our surroundings, mainly from human actions. This affects people, animals, and other organisms. Harmful substances causing pollution are called pollutants. Pollutants are released into nature in large amounts. They disrupt ecosystems and contaminate air, water, or soil.

Pollutants are classified in various ways. Biodegradable pollutants, like sewage, can be broken down by microbes. Non-biodegradable pollutants, like plastic and pesticides, degrade very slowly or not at all. Primary pollutants, such as smoke or carbon dioxide, enter the environment directly from sources. Secondary pollutants, like smog or ozone, form when primary pollutants react in the air, often becoming more toxic. Quantitative pollutants, like carbon dioxide, exist naturally but become harmful in large amounts. Qualitative pollutants, like pesticides, are man-made and not naturally found in the environment.

Different environmental parts suffer from pollution. Air pollution occurs when too much foreign matter, like harmful gases or dust, is in the air. This harms humans, animals, and plants. Water pollution alters water’s characteristics, making it unfit for use. Waste from homes, industries, or farms contaminates rivers, lakes, and oceans. This reduces oxygen, harms aquatic life, and can spread diseases. Marine pollution can create ‘dead zones’. These are ocean areas with too little oxygen for most sea life. Soil pollution happens when harmful substances contaminate the soil. This can be from industrial waste or overuse of fertilizers. It reduces soil fertility and can transfer pollutants into our food through plants.

Radioactive pollution is an increase in natural background radiation due to human activities. These activities involve using radioactive materials for nuclear weapons or power. Nuclear accidents, such as at Chernobyl, release dangerous radiation. This radiation stays harmful for centuries and causes serious health risks.

Noise pollution is unwanted sound that irritates and causes stress. Loud sounds are generally considered noise. Noise pollution directly affects people, even if it doesn’t harm air, soil, or water directly. Constant loud noise can reduce sleep, lower work efficiency, and disturb peace. Common sources include industries, traffic, and loud speakers.

Textbook solutions (Morning Star/Total)

Multiple-Choice Questions

1. Any change in the natural quality of the environment brought about chemical, physical or biological factors:

(a) Pollution
(b) Dust
(c) Humidity
(d) Pollutants

Answer: (a) Pollution

2. The products which are released into the biosphere in large quantities and which affect the normal functioning of ecosystems:

(a) Pollution
(b) Dust
(c) Humidity
(d) Pollutants

Answer: (d) Pollutants

3. Any unfavourable alteration of our surroundings, wholly or largely as a byproduct of man’s actions:

(a) Pollution
(b) Environmental Pollution
(c) Humidity
(d) Pollutants

Answer: (b) Environmental Pollution

4. The alteration in characteristics of water, making it unsuitable for designated use in its natural state:

(a) Air Pollution
(b) Water Pollution
(c) Soil Pollution
(d) Radioactive Pollution

Answer: (b) Water Pollution

5. The pollutants which are formed from the chemical reaction of primary pollutants in the environment:

(a) Biodegradable pollutants
(b) Secondary pollutants
(c) Quantitative pollutants
(d) Non-Biodegradable pollutants

Answer: (b) Secondary pollutants

6. The excessive concentration of foreign matter in the air which adversely affects the well-being of human beings, animals, plants and their environment:

(a) Air Pollution
(b) Pollution
(c) Soil Pollution
(d) Radioactive Pollution

Answer: (a) Air Pollution

7. The pollutants which are not degraded by microbes or degrade at a very slow rate:

(a) Biodegradable pollutants
(b) Primary pollutants
(c) Quantitative pollutants
(d) Non-Biodegradable pollutants

Answer: (d) Non-Biodegradable pollutants

8. Unwanted sound that is an irritant and source of stress:

(a) Air pollution
(b) Radioactive pollution
(c) Noise pollution
(d) Soil pollution

Answer: (c) Noise pollution

9. Which of the following is an example of soil pollution?

(a) Disposal of solid waste in the open
(b) Dumping sewage in the open
(c) Overuse of fertilizers
(d) All of the above.

Answer: (d) All of the above.

10. Nuclear fuels produce pollution by

(a) heat
(b) end products
(c) wastes in coolants
(d) All of the above.

Answer: (d) All of the above.

Short Answer Questions

1. What is environmental pollution? What is a pollutant?

Answer: Environmental pollution refers to any unfavourable alteration of our surroundings, wholly or largely as a byproduct of man’s actions. These changes may affect man and other organisms.

A pollutant is a substance present in the environment in harmful concentration which contaminates air, water or soil. Pollutants are the products which are released into the biosphere in large quantities and which affect the normal functioning of ecosystems and have an adverse effect on plants, animals and man. They affect adversely the environment, human beings and other organisms.

2. Give the difference between natural and man-made pollutants.

Answer: The difference between natural and man-made pollutants lies in their origin. Pollution may be natural, originating from sources like volcanic eruptions, or it can be anthropogenic or man-made, such as from industrial pollution. Man-made pollutants are often introduced into the environment through man’s activities; for example, qualitative pollutants like pesticides (DDT), chemical fertilizers, and herbicides do not naturally exist in the environment. In contrast, natural pollutants originate from natural processes or sources.

3. What is air pollution? Give a source of air pollution.

Answer: Air pollution is defined as the excessive concentration of foreign matter in the air which adversely affects the well-being of human beings, animals, plants and their environment.

A source of air pollution is automobiles, which release primary pollutants such as Nitrogen oxides and hydrocarbons.

4. Define water pollution.

Answer: Water pollution is the alteration in physical, chemical or biological characteristics of water, making it unsuitable for designated use in its natural state. The World Health Organization (WHO) has also defined water pollution as any foreign material either from natural or other sources that may contaminate the water supply and make it harmful to life.

5. What is soil pollution? Why should we avoid soil pollution?

Answer: Soil pollution is defined as the change in physical, chemical and biological conditions of the soil through man’s intervention resulting in degradation in quality and productivity of the soil.

We should avoid soil pollution because it results in the degradation in quality and productivity of the soil. Additionally, the pollutants enter the food chain at the plant level and get magnified as we move up the food chain. Soil pollution also differs from water and air pollutions in the sense that the pollutants remain in the soil for relatively longer periods.

6. What is radioactive pollution?

Answer: Radioactive pollution is defined as the increase in natural background radiation, emerging from the activities of man using naturally occurring or artificially produced radioactive materials.

7. What is noise pollution?

Answer: Noise pollution is defined as an unwanted sound that is an irritant and a source of stress.

Structured Questions

1. (a) With reference to pollution, explain the following:
(i) Air pollution

Answer: Air pollution is defined as the excessive concentration of foreign matter in the air which adversely affects the well-being of human beings, animals, plants and their environment.

(ii) Water pollution.

Answer: Water pollution can be defined as alteration in physical, chemical or biological characteristics of water, making it unsuitable for designated use in its natural state. WHO has defined water pollution as any foreign material either from natural or other sources that may contaminate the water supply and make it harmful to life.

(b) Explain what is radioactive pollution.

Answer: Radioactive pollution is defined as the increase in natural background radiation, emerging from the activities of man using naturally occurring or artificially produced radioactive materials.

(c) What are man-made causes of radioactive pollution? Why is radioactive pollution more harmful than other types of pollution?

Answer: Man-made causes of radioactive pollution originate from the use of radioactive materials. These materials are used in the production of nuclear weapons and nuclear fuel. The radioactive material used in atom bombs is very destructive. Nuclear fuels in atomic reactors produce pollution. During this process, two types of wastes are formed: (i) the fission products remaining in both the primary and secondary fuels, and (ii) waste products in the coolant. The disposal of radioactive wastes causes pollution. Leakage in nuclear reactors causes environmental pollution.

Radioactive pollution is harmful because the radioactive material used in atom bombs is very destructive. We are aware of the impact of radioactivity on man and environment during the Second World War when the US dropped atom bombs on Hiroshima and Nagasaki in Japan in August 1945. The high level products of nuclear wastes remain in the environment for several hundred years. Leakage in nuclear reactors may result in the death of a number of people as happened at Chernobyl Atomic Reactor in the erstwhile USSR on April 26, 1986.

(d) How is noise a source of pollution? Why do we need to look at the problem of noise pollution seriously?

Answer: Noise is a source of pollution as it is an unwanted sound that is an irritant and a source of stress. Noise is a physical form of pollution which is not directly harmful to the life supporting systems namely air, soil and water; its effects are more directly felt by the receiver, i.e., man.

We need to look at the problem of noise pollution seriously, because although noise pollution is not fatal to human life, yet its effects cannot be overlooked because (i) repeated exposure to noise reduces the sleeping hours (ii) productivity or efficiency of a human being (iii) it affects the peace of mind and invades the privacy of a human being.

Thinking Skills

1. Which type/types of pollution is/are more prominent in the city where you live? List the causes and possible remedies.

Answer: In the city where I live, air and noise pollution are the most prominent types of pollution.

Causes of air pollution:

• Emissions from vehicles such as cars, buses, and motorcycles release harmful gases like carbon monoxide, sulphur dioxide, and nitrogen oxides.
• Industrial activities release smoke and chemical fumes into the atmosphere.
• Burning of garbage and use of firecrackers during festivals further degrade air quality.

Remedies:

• Promoting public transport, carpooling, and the use of electric vehicles to reduce emissions.
• Enforcing stricter emission norms for industries and encouraging the use of cleaner technologies.
• Planting more trees to absorb pollutants and improve air quality.

Causes of noise pollution:

• Heavy traffic on roads, honking of horns, and loudspeakers during events.
• Industrial machinery and construction work generate continuous loud sounds.
• Household appliances and entertainment systems contribute to indoor noise pollution.

Remedies:

• Creating silent zones around hospitals, schools, and residential areas.
• Regulating the use of loudspeakers and enforcing limits on noise levels.
• Encouraging people to use noise-reducing technologies and adopt quieter alternatives.

2. Environmental pollution is an incurable disease which can only be prevented. Justify this statement giving examples.

Answer: Environmental pollution causes long-lasting and often irreversible damage to nature and human health. For example, once harmful chemicals enter the soil or water, they remain for years, affecting crops, animals, and people. Pollutants like plastic and radioactive waste do not degrade easily and can harm living beings for decades.

Prevention is the only effective solution. If we avoid using plastic bags and switch to eco-friendly alternatives, we prevent soil and water pollution. If factories treat their waste before releasing it into rivers, water bodies remain clean and safe for marine life and humans. Similarly, using clean energy sources like solar power can prevent air pollution caused by burning fossil fuels.

Thus, just like a disease that cannot be cured once it has spread too far, pollution cannot be undone easily. The best way to protect our environment is to stop pollution before it starts.

Practical Work

Write down five harmful effects of using non-biodegradable products like plastic bags. Suggest measures that can help to replace plastic bags with eco-friendly products.

Answer: Five harmful effects of using non-biodegradable products like plastic bags:

• They remain in the environment for a very long time as they degrade very slowly or not at all.
• They pollute the soil and reduce its fertility, which affects plant growth.
• When thrown into water bodies, they cause water pollution and harm aquatic life.
• Animals may eat plastic bags by mistake, which can cause injury or even death.
• The production and burning of plastic bags release toxic gases, contributing to air pollution.

Measures to replace plastic bags with eco-friendly alternatives:

• Use cloth bags or jute bags when shopping.
• Reuse old bags and avoid buying new plastic ones.
• Spread awareness in schools and communities about using alternatives.
• Support shops and companies that use biodegradable packaging.
• Request authorities to ban single-use plastic in schools and public places.

Extras

Additional MCQs

1. What best defines environmental pollution?

A. Unfavourable environmental alteration
B. Reduction in biodiversity
C. Natural ecosystem process
D. Increase in vegetation

Answer: A. Unfavourable environmental alteration

2. What is a pollutant?

A. Harmful environmental substance
B. Beneficial ecosystem component
C. Natural air constituent
D. Renewable resource

Answer: A. Harmful environmental substance

3. Which pollutant can be degraded by microbial action?

A. Biodegradable pollutant
B. Non-biodegradable pollutant
C. Secondary pollutant
D. Qualitative pollutant

Answer: A. Biodegradable pollutant

4. Which pollutant degrades very slowly?

A. Non-biodegradable pollutant
B. Primary pollutant
C. Quantitative pollutant
D. Biodegradable pollutant

Answer: A. Non-biodegradable pollutant

5. Which pollutant is directly released from its source into the environment?

A. Primary pollutant
B. Secondary pollutant
C. Qualitative pollutant
D. Thermal pollutant

Answer: A. Primary pollutant

6. Which pollutant forms through reactions of other pollutants?

A. Secondary pollutant
B. Primary pollutant
C. Biodegradable pollutant
D. Quantitative pollutant

Answer: A. Secondary pollutant

7. Which pollutant exists naturally but becomes harmful at high concentration?

A. Quantitative pollutant
B. Qualitative pollutant
C. Primary pollutant
D. Noise pollutant

Answer: A. Quantitative pollutant

8. Which pollutant is introduced only by human activities?

A. Qualitative pollutant
B. Quantitative pollutant
C. Secondary pollutant
D. Air pollutant

Answer: A. Qualitative pollutant

9. What term describes excessive foreign matter in the air?

A. Air pollution
B. Water pollution
C. Soil pollution
D. Noise pollution

Answer: A. Air pollution

10. Which of the following is a primary pollutant gas?

A. Carbon monoxide
B. Ozone
C. PAN
D. Water vapour

Answer: A. Carbon monoxide

11. What is the alteration making water unsuitable for its designated use?

A. Water pollution
B. Soil pollution
C. Air pollution
D. Noise pollution

Answer: A. Water pollution

12. WHO defines water pollution as foreign material that does what?

A. Makes water harmful
B. Raises water pH
C. Increases clarity
D. Lowers temperature

Answer: A. Makes water harmful

13. In worst cases, marine pollution creates what?

A. Dead zones
B. Coral reefs
C. Sandy beaches
D. Freshwater springs

Answer: A. Dead zones

14. What percentage of marine pollution originates from land?

A. 80%
B. 20%
C. 50%
D. 100%

Answer: A. 80%

15. Mining for which materials is a major source of ocean contamination?

A. Copper and gold
B. Iron and coal
C. Silver and tin
D. Aluminium and nickel

Answer: A. Copper and gold

16. What defines soil pollution?

A. Change in soil conditions
B. Excessive water use
C. Airborne dust deposition
D. Noise from machinery

Answer: A. Change in soil conditions

17. Change in environmental temperature causing pollution is called what?

A. Thermal pollution
B. Dust pollution
C. Noise pollution
D. Gaseous pollution

Answer: A. Thermal pollution

18. Pollution by particulate matter is known as what?

A. Dust pollution
B. Thermal pollution
C. Noise pollution
D. Radioactive pollution

Answer: A. Dust pollution

19. Pollution involving chemical gases is termed what?

A. Gaseous pollution
B. Soil pollution
C. Dust pollution
D. Noise pollution

Answer: A. Gaseous pollution

20. Pollution from unwanted sound is called what?

A. Noise pollution
B. Thermal pollution
C. Radioactive pollution
D. Water pollution

Answer: A. Noise pollution

21. Pollution due to radioactive materials is called what?

A. Radioactive pollution
B. Thermal pollution
C. Gaseous pollution
D. Dust pollution

Answer: A. Radioactive pollution

22. Pollution in the hydrosphere is known as what?

A. Water pollution
B. Air pollution
C. Soil pollution
D. Noise pollution

Answer: A. Water pollution

23. Pollution in the lithosphere is known as what?

A. Soil pollution
B. Air pollution
C. Water pollution
D. Noise pollution

Answer: A. Soil pollution

24. Pollution in the atmosphere is known as what?

A. Air pollution
B. Water pollution
C. Soil pollution
D. Noise pollution

Answer: A. Air pollution

25. Pollution from volcanic eruptions is classified as what?

A. Natural pollution
B. Anthropogenic pollution
C. Primary pollution
D. Secondary pollution

Answer: A. Natural pollution

26. Pollution from factory emissions is called what?

A. Anthropogenic pollution
B. Natural pollution
C. Primary pollution
D. Secondary pollution

Answer: A. Anthropogenic pollution

27. Which of the following is a secondary pollutant?

A. Ozone
B. Carbon monoxide
C. Sulphur dioxide
D. Methane

Answer: A. Ozone

28. Which hydrocarbon is a primary pollutant?

A. Benzene
B. Ozone
C. PAN
D. Sulphur dioxide

Answer: A. Benzene

29. Freshwater pollution arises from which sources?

A. Domestic effluents
B. Industrial effluents
C. Agricultural effluents
D. All of the above

Answer: D. All of the above

30. Polluted freshwater is unfit for which uses?

A. Drinking
B. Swimming
C. Fishing
D. All of the above

Answer: D. All of the above

31. Which activity produces man-made radiation?

A. Nuclear weapons
B. Volcanic eruptions
C. Vehicle emissions
D. Solar panels

Answer: A. Nuclear weapons

32. Atomic bombings of Hiroshima and Nagasaki in August 1945 illustrate which pollution?

A. Radioactive pollution
B. Thermal pollution
C. Air pollution
D. Noise pollution

Answer: A. Radioactive pollution

33. High-level nuclear wastes remain in the environment for how long?

A. Several hundred years
B. A few days
C. Many decades
D. Thousands of years

Answer: A. Several hundred years

34. Leakage from which 1986 reactor caused severe radioactive pollution?

A. Chernobyl reactor
B. Fukushima reactor
C. Three Mile Island
D. Sellafield plant

Answer: A. Chernobyl reactor

35. Which of the following is a waste product formed in nuclear reactors?

A. Fission products
B. Agricultural runoff
C. Domestic garbage
D. Industrial smoke

Answer: A. Fission products

Additional Assertion and Reason

1. Assertion (A): The term ‘pollution’ refers to any change in the natural quality of the environment.
Reason (R): This change is brought about by chemical, physical or biological factors.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (a) Both A and R are true and R is the correct explanation of A.

2. Assertion (A): Pollutants are products which are released into the biosphere in large quantities.
Reason (R): They affect the normal functioning of ecosystems and have an adverse effect on plants, animals and man.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (a) Both A and R are true and R is the correct explanation of A.

3. Assertion (A): Secondary pollutants are formed from the chemical reaction of primary pollutants in the environment.
Reason (R): Peroxyacetyl Nitrate (PAN) and Ozone are examples of secondary pollutants.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (a) Both A and R are true and R is the correct explanation of A.

4. Assertion (A): Quantitative pollutants exist in nature but they act as pollutants when their concentration or quantity increases up to a critical level.
Reason (R): Carbon dioxide and Nitrogen oxide are examples of quantitative pollutants.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (a) Both A and R are true and R is the correct explanation of A.

5. Assertion (A): Radioactive pollution is defined as the increase in natural background radiation.
Reason (R): This increase emerges from the activities of man using naturally occurring or artificially produced radioactive materials.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (a) Both A and R are true and R is the correct explanation of A.

6. Assertion (A): Primary pollutants are directly introduced by their sources into the environment.
Reason (R): Secondary pollutants are formed from the chemical reaction of primary pollutants in the environment.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (b) Both A and R are true but R does not explain A.

7. Assertion (A): Air pollution is defined as the excessive concentration of foreign matter in the air.
Reason (R): Air pollution adversely affects the well-being of human beings.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (b) Both A and R are true but R does not explain A.

8. Assertion (A): Water pollution is defined as alteration in physical, chemical or biological characteristics of water.
Reason (R): Pollution of water leads to reduction of normal oxygen level of water.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (b) Both A and R are true but R does not explain A.

9. Assertion (A): Soil pollution is defined as the change in physical, chemical and biological conditions of the soil.
Reason (R): The pollutants enter the food chain at the plant level due to soil pollution.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (b) Both A and R are true but R does not explain A.

10. Assertion (A): Noise pollution is defined as an unwanted sound that is an irritant and a source of stress.
Reason (R): Repeated exposure to noise reduces the sleeping hours.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (b) Both A and R are true but R does not explain A.

11. Assertion (A): Biodegradable pollutants are the pollutants which can be degraded by biological or microbial actions.
Reason (R): Glass and plastics are examples of biodegradable pollutants.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (c) A is true but R is false

12. Assertion (A): Non-biodegradable pollutants are the pollutants which are not degraded by microbes or degrade at a very slow rate.
Reason (R): Sewage and domestic garbage are examples of non-biodegradable pollutants.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (c) A is true but R is false

13. Assertion (A): Air pollution is defined as the excessive concentration of foreign matter in the air.
Reason (R): This foreign matter only affects non-living things.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (c) A is true but R is false

14. Assertion (A): Water pollution is defined as alteration in physical, chemical or biological characteristics of water.
Reason (R): This alteration makes it suitable for designated use in its natural state.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (c) A is true but R is false

15. Assertion (A): Soil pollution is defined as the change in physical, chemical and biological conditions of the soil.
Reason (R): This change results in improvement in quality and productivity of the soil.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (c) A is true but R is false

16. Assertion (A): Quantitative pollutants do not exist in environment.
Reason (R): They act as pollutants when their concentration or quantity increases up to a critical level in the atmosphere.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (d) A is false but R is true

17. Assertion (A): Qualitative pollutants exist in nature but they act as pollutants when their concentration increases.
Reason (R): Pesticides (DDT) and chemical fertilizers are examples of qualitative pollutants.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (d) A is false but R is true

18. Assertion (A): Man-made radiations originate from cosmic radiations from the outer space.
Reason (R): Cosmic radiations are a type of environmental radiation.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (d) A is false but R is true

19. Assertion (A): Noise pollution is fatal to human life.
Reason (R): Repeated exposure to noise reduces the sleeping hours.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (d) A is false but R is true

20. Assertion (A): Eighty per cent of marine pollution comes from the ocean itself.
Reason (R): Mining for materials such as copper and gold is a major source of contamination in the ocean.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false
(d) A is false but R is true

Answer: (d) A is false but R is true