Question

what does water react with in the atmosphere to form carbonic acid to make regular rainfall slightly acidic? ozone carbon dioxide lead nitrogen gas

Explanation:

Water reacts with carbon - dioxide in the atmosphere to form carbonic acid. The chemical reaction is $H_2O + CO_2
ightleftharpoons H_2CO_3$. This makes regular rainfall slightly acidic. Ozone, lead, and nitrogen gas do not react with water to form carbonic acid in the context of making rain acidic.

Answer:

carbon dioxide