Rain is called acid rain when its pH is below
A. 7
B. 6.5
C. 6
D. 4 to 5

Hint: Acid rain is an acidic rain, which means it has a very low pH. On trees, freshwater (lakes or rivers), and soils, acid rain has dangerous causes. They kill aquatic life forms and insects, cause peeling of paint, damage to steel structures such as bridges, weathering of stone structures and sculptures, and have an effect on human health.

Complete answer:
Acid rain is a broad term that includes any type of acid component precipitation, such as sulfuric acid or nitric acid, which, in wet or dry forms, falls from the atmosphere to the ground. This can be of any type like acidic rain, snow, fog, hail, or even dust. Rainfall and other types of precipitation with a pH lower than 6.0 pH are acid rain. The large-scale release of acidic gases from thermal power plants, factories, and vehicles into the atmosphere triggers it. Acid rain is a common term that refers to the deposition of a mixture of acidic components from wet and dry. Distilled water has a neutral pH of 7 until carbon dioxide is extracted. Liquids with a pH below 7 are acidic, while liquids with a pH above 7 are alkaline. But typically not less than 5.7, since carbon dioxide and water in the air react together to form carbonic pH. They combine with water and oxygen when sulfur dioxide and nitrogen oxides are released into the air and create sulfuric and nitric acids. Then these acids combine with water, resulting in acid rain. With a pH range of 5-6, natural rainwater is mildly acidic. It becomes acid rain when the pH level of rainwater falls below this range. Therefore, the pH of acid rain is approximately 4 to 5.

So, option D) is the correct option.

Note: Energy production without using fossil fuels is a perfect way to decrease acid rain. People may use renewable sources of energy, such as solar and wind power, instead. Since they contain much fewer emissions, renewable energy sources help mitigate acid rain. It can affect plants, aquatic animals, and facilities in a harmful way.