Pollution of Air and Water Part 4: MCQs (Q76–Q100)
🌍 Pollution of Air and Water – MCQs for Class 8 Science
Part 4: Q76–Q100
Q76. Which pollutant is mainly responsible for global warming?
A) Oxygen
B) Carbon dioxide
C) Nitrogen
D) Helium
✅ Correct Answer: B) Carbon dioxide
Explanation:
- B) ✔ CO₂ traps heat in the atmosphere → rise in global temperatures.
- A, C, D) Do not significantly contribute to global warming.
Q77. Which of these is NOT a water pollutant?
A) Oil spill
B) Fertilizers
C) Plastics
D) Oxygen
✅ Correct Answer: D) Oxygen
Explanation:
- D) ✔ Oxygen is essential for aquatic life, not a pollutant.
Q78. Which disease is caused by fluoride-contaminated water?
A) Cholera
B) Fluorosis
C) Typhoid
D) Dysentery
✅ Correct Answer: B) Fluorosis
Explanation:
- B) ✔ Excess fluoride causes yellowing of teeth and bone damage.
Q79. Which pollutant is the major cause of photochemical smog?
A) SO₂
B) NO₂
C) Ozone
D) Dust
✅ Correct Answer: B) NO₂
Explanation:
- B) ✔ Nitrogen oxides + hydrocarbons + sunlight → photochemical smog.
Q80. Which international day is observed for environmental protection?
A) June 5
B) April 22
C) March 22
D) December 1
✅ Correct Answer: A) June 5
Explanation:
- A) ✔ World Environment Day is celebrated on June 5.
- B) April 22 = Earth Day.
- C) March 22 = World Water Day.
- D) December 1 = World AIDS Day.
Q81. The main pollutant released from burning coal is:
A) Oxygen
B) Sulphur dioxide
C) Nitrogen
D) Argon
✅ Correct Answer: B) Sulphur dioxide
Explanation:
- B) ✔ Coal combustion releases SO₂ → acid rain.
Q82. Excessive growth of algae in water bodies is caused by:
A) Oxygen
B) Nutrients like nitrates
C) CO₂
D) Methane
✅ Correct Answer: B) Nutrients like nitrates
Explanation:
- B) ✔ Nutrient pollution causes eutrophication → algal bloom.
Q83. Which gas is called a “greenhouse gas” but also used in fire extinguishers?
A) Carbon dioxide
B) Oxygen
C) Nitrogen
D) Methane
✅ Correct Answer: A) Carbon dioxide
Explanation:
- A) ✔ CO₂ both traps heat and extinguishes fires by cutting oxygen supply.
Q84. Which is the main source of water pollution in cities?
A) Rainwater
B) Industrial waste and sewage
C) Rocks
D) Soil
✅ Correct Answer: B) Industrial waste and sewage
Explanation:
- B) ✔ Factories and untreated sewage are major contributors.
Q85. Which pollutant reduces the oxygen-carrying capacity of blood?
A) Carbon monoxide
B) Nitrogen
C) Sulphur dioxide
D) Argon
✅ Correct Answer: A) Carbon monoxide
Explanation:
- A) ✔ CO binds with haemoglobin, blocking oxygen transport.
Q86. Which of these is a noise pollution control measure?
A) Planting trees
B) More vehicle horns
C) Burning crackers
D) Loudspeakers
✅ Correct Answer: A) Planting trees
Explanation:
- A) ✔ Trees act as noise barriers.
Q87. Which layer of the atmosphere contains ozone?
A) Troposphere
B) Stratosphere
C) Mesosphere
D) Exosphere
✅ Correct Answer: B) Stratosphere
Explanation:
- B) ✔ Ozone layer lies in the stratosphere, protecting from UV rays.
Q88. The main cause of eutrophication is:
A) Oil spills
B) Excess fertilizers
C) Industrial gases
D) Noise
✅ Correct Answer: B) Excess fertilizers
Explanation:
- B) ✔ Runoff of fertilizers increases nutrients → algal blooms.
Q89. The term “smog” is formed from:
A) Smoke + gas
B) Smoke + fog
C) Smoke + oxygen
D) Snow + gas
✅ Correct Answer: B) Smoke + fog
Explanation:
- B) ✔ Smog = smoke + fog, reduces visibility and affects health.
Q90. Which chemical in plastics makes them non-biodegradable?
A) Hydrocarbons
B) Chlorine
C) Polyethylene
D) Dioxins
✅ Correct Answer: C) Polyethylene
Explanation:
- C) ✔ Polyethylene chains resist natural decomposition.
Q91. The Bhopal Gas Tragedy was caused by leakage of:
A) Methane
B) Methyl isocyanate
C) Sulphur dioxide
D) Ozone
✅ Correct Answer: B) Methyl isocyanate
Explanation:
- B) ✔ MIC gas leak in 1984 caused thousands of deaths.
Q92. Which river cleaning project was launched in 1985?
A) Yamuna Action Plan
B) Ganga Action Plan
C) Godavari Plan
D) Narmada Plan
✅ Correct Answer: B) Ganga Action Plan
Explanation:
- B) ✔ GAP aimed to reduce pollution in River Ganga.
Q93. Which pollutant causes the “Greenhouse Effect”?
A) CO₂, CH₄, N₂O
B) O₂, H₂, N₂
C) Ar, Ne, He
D) SO₂ only
✅ Correct Answer: A) CO₂, CH₄, N₂O
Explanation:
- A) ✔ Carbon dioxide, methane, nitrous oxide are main greenhouse gases.
Q94. Which of these is an example of secondary air pollutant?
A) Carbon monoxide
B) Sulphur dioxide
C) Ozone
D) Methane
✅ Correct Answer: C) Ozone
Explanation:
- C) ✔ Ozone forms when sunlight reacts with primary pollutants.
Q95. Which of the following diseases is NOT caused by water pollution?
A) Cholera
B) Typhoid
C) Asthma
D) Dysentery
✅ Correct Answer: C) Asthma
Explanation:
- C) ✔ Asthma is caused by air pollution, not water pollution.
Q96. Which gas is responsible for acidification of oceans?
A) Oxygen
B) Carbon dioxide
C) Nitrogen
D) Methane
✅ Correct Answer: B) Carbon dioxide
Explanation:
- B) ✔ Dissolved CO₂ forms carbonic acid, lowering ocean pH.
Q97. Which step can reduce vehicular pollution?
A) Overusing diesel vehicles
B) Promoting public transport
C) Using outdated engines
D) Cutting trees
✅ Correct Answer: B) Promoting public transport
Explanation:
- B) ✔ More public transport = fewer vehicles = less pollution.
Q98. Which is the main cause of ozone hole over Antarctica?
A) Excess CO₂
B) CFCs
C) Nitrogen oxides
D) Methane
✅ Correct Answer: B) CFCs
Explanation:
- B) ✔ Chlorofluorocarbons react with ozone, causing thinning.
Q99. Which of these is an effect of noise pollution?
A) Hearing loss
B) Better concentration
C) Sound sleep
D) More oxygen
✅ Correct Answer: A) Hearing loss
Explanation:
- A) ✔ Noise pollution leads to stress, deafness, and lack of concentration.
Q100. Which of these practices helps reduce water pollution?
A) Dumping untreated sewage
B) Using eco-friendly detergents
C) Throwing plastic into rivers
D) Using pesticides excessively
✅ Correct Answer: B) Using eco-friendly detergents
Explanation:
- B) ✔ Eco-friendly detergents degrade easily and do not pollute water.
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