Reason: Acid rain contains acids like nitric acid, which corrodes the upper layer of buildings and monuments.
Both the statement and the reason are correct and the reason is the correct explanation of the statement.
The rain becomes acidic because carbon dioxide, sulphur dioxide and nitrogen dioxide (which are released into the air as pollutants) dissolve in rain drops to form carbonic acid, sulphuric acid and nitric acid respectively. Acid rain can cause damage to buildings, historical monuments because they react with the material in the upper layer of the buildings or monuments and corrodes them. They also damage plants and animals by damaging the upper layer of their skin.