Unit 5 — MCQ Practice Bank: 28 questions based on the official MGSU syllabus and PYQ analysis. Tap Show Answer to check yourself. 🔥 = high priority, ⭐ = important.
Q1. Which of the following best describes a "pollutant"? Expected
- Any substance found naturally in the environment
- A substance or form of energy present in the environment in quantities that harm life
- Only gases released by factories
- Only chemicals that can be recycled
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Answer: B — A pollutant is anything (smoke, sewage, pesticides, plastic, loud sound, heat, radiation) present in harmful quantities — not merely anything natural.
Q2. Which of these air pollutants is formed in the atmosphere through chemical reactions, rather than being emitted directly from a source? PYQ 2022 🔥
- Carbon monoxide
- Sulphur dioxide
- PAN (peroxyacetyl nitrate)
- Particulate matter
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Answer: C — PAN is a secondary pollutant, formed when primary pollutants react in the atmosphere; CO, SO2 and particulates are emitted directly (primary).
Q3. The Union Carbide plant at Bhopal, from which toxic gas leaked on the night of 2–3 December 1984, manufactured which type of product? PYQ 2023 🔥
- Pesticides
- Fertilisers
- Medicines
- Cement
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Answer: A — The Bhopal plant was a pesticide plant; the leaked methyl isocyanate (MIC) was a raw material used in making the pesticide carbaryl. The worst industrial disaster in history.
Q4. Acid rain is formed when sulphur dioxide and nitrogen oxides in the air react with: PYQ Dec 2024 ⭐
- Carbon dioxide
- Methane
- Ozone
- Water vapour
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Answer: D — SO2 and NOx combine with water vapour to form sulphuric and nitric acids, which fall as acid rain and damage buildings, crops and soil.
Q5. Without which of the following, photochemical smog CANNOT form? PYQ Dec 2024 🔥
- Carbon dioxide
- Sunlight
- Water vapour
- Wind
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Answer: B — Sunlight drives the reactions between NOx and hydrocarbons that produce ground-level ozone, PAN and aldehydes — that is what makes the smog "photochemical".
Q6. Carbon monoxide from vehicle exhaust is dangerous to humans mainly because it: PYQ 2022 ⭐
- Burns the lungs directly
- Dissolves in rain to form acid
- Binds with haemoglobin and blocks oxygen transport
- Increases body temperature
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Answer: C — CO binds haemoglobin to form carboxyhaemoglobin, which cannot carry oxygen — so the body's tissues are starved of oxygen.
Q7. In thermal power plants, electrostatic precipitators are fitted mainly to remove: PYQ 2023
- Particulate matter (fine dust) from chimney smoke
- Sulphur dioxide gas
- Carbon monoxide
- Waste heat
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Answer: A — Electrostatic precipitators use electric charges to trap fine dust particles from flue gases before they leave the chimney.
Q8. The National Ambient Air Quality Standards (NAAQS) in India are laid down by: Expected
- State Pollution Control Boards
- The National Green Tribunal
- The Indian Meteorological Department
- The Central Pollution Control Board (CPCB)
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Answer: D — The CPCB is the apex pollution-monitoring body, set up in 1974 under the Water Act and headquartered at New Delhi; it lays down the NAAQS.
Q9. A river sample with a very high Biochemical Oxygen Demand (BOD) indicates that the river is: PYQ 2021 🔥
- Rich in dissolved minerals
- Heavily polluted with organic waste
- Safe for drinking
- Full of clean rainwater
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Answer: B — High BOD means microbes need a lot of oxygen to decompose the organic waste present — so high BOD = more organic pollution. (Low DO also means polluted.)
Q10. Which sequence correctly describes the process of eutrophication? PYQ Dec 2024 ⭐
- Algal bloom → excess nutrients → fish death → oxygen loss
- Oxygen loss → algal bloom → excess nutrients → fish death
- Excess nutrients → algal bloom → oxygen depletion → fish death
- Fish death → excess nutrients → algal bloom → oxygen depletion
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Answer: C — Extra nitrates/phosphates trigger an algal bloom on the surface; the algae die and their decomposition consumes dissolved oxygen, killing the fish.
Q11. Pesticide-laden runoff from farmlands entering a river is an example of: Expected
- Non-point source pollution
- Point source pollution
- Thermal pollution
- Noise pollution
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Answer: A — Runoff comes from a large diffused area with no single identifiable spot, so it is a non-point source — hard to trace and control, unlike a factory pipe (point source).
Q12. Infants who drink water with excess nitrates develop a bluish skin colour. The medical name for this condition (Blue Baby Syndrome) is: PYQ 2022 🔥
- Anaemia
- Minamata disease
- Fluorosis
- Methemoglobinemia
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Answer: D — Nitrates convert to nitrites in the body, which bind haemoglobin and starve the infant's blood of oxygen — the skin turns bluish.
Q13. The Ganga Action Plan, launched in 1986, was India's first major programme aimed at: PYQ 2022
- Building dams on the Ganga
- Cleaning the river Ganga
- Generating hydropower
- Linking rivers
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Answer: B — Launched in 1986, the Ganga Action Plan focused on sewage and industrial effluent treatment to clean the river Ganga.
Q14. DDT sprayed on crops is dangerous to humans mainly because it is non-biodegradable and: Expected ⭐
- Dissolves quickly in water and disappears
- Kills all bacteria in the soil permanently
- Concentrates at each step up the food chain (biomagnification)
- Converts into harmless compost within days
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Answer: C — Non-biodegradable pollutants like DDT and mercury get more concentrated at every trophic level — top predators, including humans, receive the highest dose.
Q15. Cleaning up contaminated soil by using microbes or plants is called: Expected
- Bioremediation
- Incineration
- Landfilling
- Composting
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Answer: A — Bioremediation uses living organisms (microbes or plants) to break down or absorb pollutants from contaminated soil.
Q16. "Silence zones" are declared around which of the following places to protect people from noise pollution? Expected
- Bus terminals and airports
- Industrial estates
- Railway stations
- Schools and hospitals
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Answer: D — Silence zones are maintained near schools and hospitals, where noise disturbs learning and patient recovery the most.
Q17. Prolonged exposure to noise levels above about 85 dB can: PYQ Dec 2024
- Improve concentration
- Cause permanent hearing damage
- Lower blood pressure
- Strengthen immunity
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Answer: B — Prolonged exposure above ~85 dB damages hearing; noise pollution also causes hypertension, stress and sleep disturbance.
Q18. Thermal power plants control thermal pollution by: Expected ⭐
- Releasing hot water directly into the river at night
- Adding chemicals to cool the river
- Cooling the water in cooling towers before discharge
- Building taller chimneys
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Answer: C — Cooling towers and cooling ponds cool the hot water before discharge; hot water holds less dissolved oxygen and kills or drives away aquatic organisms.
Q19. The MARPOL convention (1973/78) is an international agreement to prevent pollution of the: Expected
- Seas and oceans from ships
- Atmosphere from vehicles
- Rivers from sewage
- Soil from pesticides
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Answer: A — MARPOL targets ship pollution (oil spills, waste dumping into seas); control measures include double-hull tankers and a ban on ocean dumping.
Q20. The worst nuclear accident in history took place at Chernobyl in the year: PYQ
- 1975
- 1979
- 1986
- 2011
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Answer: C — Chernobyl (Ukraine, then USSR) in 1986 was the worst nuclear accident ever; Three Mile Island (USA) was 1979 and Fukushima (Japan) was 2011.
Q21. The 2011 Fukushima nuclear disaster in Japan was triggered by: Expected
- A volcanic eruption
- A tsunami
- A factory fire
- A lightning strike
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Answer: B — The Fukushima plant was crippled after a tsunami in 2011; radiation effects include cancer, genetic mutations and birth defects.
Q22. Among the alpha, beta and gamma radiations emitted by radioactive materials, the most penetrating is: Expected
- Alpha radiation
- Beta radiation
- Gamma radiation
- Ultraviolet radiation
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Answer: C — Gamma rays are the most penetrating, which is why nuclear waste must be disposed of in shielded containers buried deep underground.
Q23. In the 4R waste hierarchy (Refuse → Reduce → Reuse → Recycle), which is the most preferred first step? PYQ 2023 🔥
- Refuse — say no to waste
- Recycle — make new
- Dispose — last resort
- Incinerate — burn waste
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Answer: A — The hierarchy order matters: Refuse comes first (best), disposal is the last resort; treatment methods like incineration sit in between.
Q24. The toxic liquid that oozes out of garbage dumps and can contaminate groundwater is called: Expected
- Effluent
- Slurry
- Runoff
- Leachate
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Answer: D — Leachate is the toxic liquid oozing from garbage; its seepage into groundwater is one of the main harms of poor solid-waste disposal.
Q25. Discarded electronics (e-waste) are a special concern mainly because they contain: PYQ 2022 ⭐
- Valuable diamonds
- Toxic heavy metals such as lead and mercury
- Only biodegradable plastic
- Medicinal chemicals
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Answer: B — Old electronics contain heavy metals like lead and mercury, which are toxic, non-biodegradable and can biomagnify through the food chain.
Q26. Vermicomposting converts organic kitchen waste into manure with the help of: PYQ 2023
- Chemical fertilisers
- Hot-air dryers
- Earthworms
- Electric shredders
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Answer: C — Vermicomposting uses earthworms to break down organic waste into nutrient-rich manure.
Q27. The National Disaster Management Authority (NDMA), India's apex body for disaster management, is headed by: Expected
- The Prime Minister
- The President
- The Home Minister
- The Chief Justice
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Answer: A — The NDMA, set up under the Disaster Management Act 2005, is headed by the Prime Minister of India.
Q28. The magnitude (strength) of an earthquake is measured on the: Expected
- Beaufort scale
- Mercalli scale
- Decibel scale
- Richter scale
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Answer: D — Earthquake magnitude is measured on the Richter scale; earthquakes result from the sudden release of energy along fault lines.