Answer: SO 2 and NOx from burning fossil fuels dissolving in rain to form sulphuric and nitric acids.
- A Carbon dioxide gradually dissolving in rainwater to form a mild carbonic acid solution
- B SO<sub>2</sub> and NOx from burning fossil fuels dissolving in rain to form sulphuric and nitric acids
- C Methane in the atmosphere slowly reacting with moisture present in the stratosphere
- D Ozone depletion gradually allowing excess UV radiation to reach low-level rainclouds
Correct answer: B. SO<sub>2</sub> and NOx from burning fossil fuels dissolving in rain to form sulphuric and nitric acids
Explanation: Acid rain forms when SO<sub>2</sub> (from power plants, industries) and NOx (from vehicles) react with water in the atmosphere: SO<sub>2</sub> + H<sub>2</sub>O → H<sub>2</sub>SO<sub>3</sub> (sulphurous acid); 2NO<sub>2</sub> + H<sub>2</sub>O → HNO<sub>3</sub> + HNO<sub>2</sub>. Normal rain pH ~5.6; acid rain pH < 5.6. Damages forests, aquatic life, and buildings.
Sunlight passes through the atmosphere and warms the surface; the surface re-radiates this energy as infrared heat, which greenhouse gases (CO₂, CH₄, water vapour) absorb and trap - a naturally beneficial process that intensifies into global warming as gas concentrations rise from human activity.
Concept context
Pollution, global warming, ozone depletion, deforestation, and sustainability. Important for NEET and general awareness.