Acid rain is caused by emissions of sulfur dioxide ($\text{SO}_2$) and nitrogen oxides ($\text{NO}_x$), which react with water molecules in the atmosphere to produce sulfuric and nitric acids. Option analysis: (A) Methane and ozone are greenhouse gases and secondary pollutants, not the primary causes of acid precipitation. (B) Sulphur dioxide and nitrous oxides are the primary acid-forming gases. (C) Methane does not cause acid rain. (D) Carbon dioxide causes normal mild rainwater acidity ($\text{pH} \approx 5.6$), but severe acid rain is due to $\text{SO}_2$ and $\text{NO}_x$.

The National Action Plan on Climate Change (NAPCC) launched in $2008$ encompasses eight national missions: Solar, Enhanced Energy Efficiency, Sustainable Habitat, Water, Sustaining the Himalayan Ecosystem, Green India, Sustainable Agriculture, and Strategic Knowledge for Climate Change. All four listed missions are integral components. Option analysis: (A) All four missions (i), (ii), (iii), and (iv) are included in NAPCC. (B) Omits mission (i). (C) Omits missions (i) and (ii). (D) Omits missions (ii) and (iv).

Stumpage value is the commercial value of standing trees prior to felling, representing the price paid for the right to harvest timber from a forest land. Option analysis: (A) Stumpage Value is the exact economic term for the value of standing uncut timber. (B) Timber Value is a generic term. (C) Salvage Value is the value of an asset at the end of its useful life. (D) NPV is net present value of discounted cash flows.