What is the major reason why the pH of unpolluted rain is less than 7?

A. methane

B. carbon dioxide

C. nitrogen oxides

D. sulfur dioxide

B

This was one of the challenging questions on the paper. 58 % of the candidates identified carbon dioxide as the cause of acidity in unpolluted rain. The rest mainly chose either nitrogen oxides (option C) or sulfur dioxide (option D), the causes of acidity in polluted rain.