Q1. Which gas is primarily responsible for the depletion of the ozone layer?
- Sulphur dioxide
- Carbon dioxide
- Nitrogen
- Chlorofluorocarbons (CFCs)
Correct Option: 4. Chlorofluorocarbons (CFCs)
Explanation: CFCs are man-made compounds released mainly from refrigeration and air-conditioning systems. When they reach the stratosphere, they break down ozone (O₃) molecules, leading to ozone layer depletion.
Q2. Which of the following is a major pollutant from vehicles?
- PAN
- Carbon monoxide (CO)
- CFCs
- Radon
Correct Option: 2. Carbon monoxide (CO)
Explanation: Carbon monoxide is a colorless, odorless gas produced by the incomplete combustion of fuel in vehicle engines. It is highly toxic and interferes with the body’s ability to transport oxygen.
Q3. Photochemical smog is formed due to reaction of sunlight with which combination?
- Water vapor and oxygen
- Nitrogen oxides and volatile organic compounds
- Carbon dioxide and dust
- Lead and sulphur dioxide
Correct Option: 2. Nitrogen oxides and volatile organic compounds
Explanation: Photochemical smog is a secondary pollutant formed when sunlight reacts with NOₓ and VOCs released from vehicle exhausts and solvents. One of the main components of this smog is ground-level ozone.
Q4. Which of the following pollutants is most common in rural indoor air pollution?
- Formaldehyde
- Radon
- Smoke from biomass burning
- Asbestos
Correct Option: 3. Smoke from biomass burning
Explanation: In rural areas, burning of wood, dung, and crop residue in poorly ventilated kitchens leads to indoor air pollution. This smoke contains harmful pollutants like particulate matter, carbon monoxide, and polycyclic aromatic hydrocarbons.
Q5. Which classification of pollutants includes substances that cannot be broken down by natural processes?
- Biodegradable
- Secondary
- Non-biodegradable
- Quantitative
Correct Option: 3. Non-biodegradable
Explanation: Non-biodegradable pollutants are substances like plastics, heavy metals, and radioactive waste that do not decompose naturally and can persist in the environment for hundreds of years, causing long-term damage.