Acid rain is primarily caused by the emission of sulphur dioxide (SO2) and nitrogen oxides (NOx). When these gases react with water vapor in the atmosphere, they form sulphuric acid and nitric acid, respectively, which then fall to the ground as precipitation, significantly lowering the pH of the rainwater.

Smog, particularly classical or London-type smog, is primarily caused by the accumulation of sulfur dioxide (SO2) and nitrogen oxides (NOx) in the atmosphere. These pollutants react with moisture and particulate matter to create a dense, hazy layer. While photochemical smog involves additional components, oxides of nitrogen and sulfur remain the fundamental precursors for various types of smog.

The troposphere is the lowest layer of Earth's atmosphere, extending from the surface to about 8-15 kilometers in altitude. This layer contains the majority of the atmosphere's mass, including the air we breathe, and is where weather phenomena occur, making it the habitat for humans and most other living organisms.

Photochemical smog is formed through complex photochemical reactions involving nitrogen oxides (NOx), volatile organic compounds (VOCs), and sunlight. These reactions produce secondary pollutants like ozone (O3) and peroxyacetyl nitrates (PAN). The presence of sunlight is essential to trigger the dissociation of NO2, which initiates the formation of these reactive species in the troposphere.

Peroxyacetyl nitrate (PAN) is a secondary pollutant formed in the atmosphere through photochemical reactions involving nitrogen oxides and volatile organic compounds. It is a well-known lachrymator, meaning it causes significant irritation to the eyes and respiratory system in humans.

Carbon monoxide (CO) binds to hemoglobin with an affinity approximately 200 to 250 times greater than that of oxygen. This formation of carboxyhemoglobin prevents the blood from effectively transporting oxygen to tissues, leading to hypoxia. This process is a classic example of competitive binding in biological systems, where the toxic gas effectively displaces the vital oxygen molecule from the heme group.

The Earth's atmosphere is composed of approximately 78% nitrogen, 21% oxygen, and about 0.9% argon, with carbon dioxide concentrations currently ranging between 0.03% and 0.05%. Since all the provided percentages in options A, B, and C are accurate representations of the atmospheric composition, the statement that none of them are wrong is the correct choice.

The National Air Quality Index (NAQI) typically monitors pollutants such as PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Lead. Methane is a greenhouse gas but is generally not included in the standard criteria pollutants monitored for immediate air quality health indexing. Note that 'Sulphu' in option A is a typographical error for Sulphur dioxide, which is a standard monitored pollutant.

Acid rain is primarily caused by the emission of sulfur and nitrogen oxides from burning fossil fuels. Liquefied Petroleum Gas (LPG) and Compressed Natural Gas (CNG) are cleaner-burning fuels compared to coal or heavy petroleum products, as they produce significantly fewer sulfur and nitrogen pollutants, thereby mitigating acid rain formation.

Acid rain occurs when sulfur dioxide (SO2) and nitrogen oxides (NOx) are emitted into the atmosphere. These gases react with water vapor, oxygen, and other chemicals to form sulfuric acid and nitric acid, which then fall to the ground as acidic precipitation, causing environmental damage.