Consider the following statements : Statement-I: Rainfall is one of the reasons for weathering of rocks. Statement II: Rain water contains carbon dioxide in solution. Statement-III: Rain water contains atmospheric oxygen. Which one of the following is correct in respect of the above statements ?

1. A. Both Statement-II and Statement-III are correct and both of them explain Statement-I
2. B. Both Statement-II and Statement-III are correct, but only one of them explains Statement-I
3. C. Only one of the Statements II and III is correct and that explains Statement-I
4. D. Neither Statement- II nor Statement-Ill is correct

Answer: A

Explanation

Both Statement-II and Statement-III are correct, and both explain Statement-I. Rainfall is a significant agent of chemical weathering. Rainwater absorbs carbon dioxide from the atmosphere, forming carbonic acid (Statement II), which is a weak acid capable of dissolving certain minerals, especially in limestone (carbonation). Additionally, rainwater contains dissolved atmospheric oxygen (Statement III), which can react with minerals like iron in rocks (oxidation), leading to their breakdown and weakening. Both carbonation and oxidation are major chemical weathering processes facilitated by rainwater, thus explaining why rainfall is a reason for rock weathering. This question tests fundamental concepts of geomorphology.