Here's why:

* Limestone's Composition: Limestone is primarily made up of calcium carbonate (CaCO3).

* Acid Rain's Components: Acid rain contains sulfuric acid (H2SO4) and nitric acid (HNO3).

* Chemical Reaction: When acid rain falls on limestone, the acids react with the calcium carbonate, resulting in the following reaction:

CaCO3 (s) + 2H+ (aq) → Ca2+ (aq) + CO2 (g) + H2O (l)

* Result: This reaction produces carbon dioxide gas, along with calcium ions and water. The carbon dioxide bubbles out, contributing to the overall acidity of the environment.

Other gases may be produced in smaller quantities:

* Sulfur dioxide (SO2): If the acid rain is particularly strong or the limestone is impure, some sulfur dioxide may be released.

* Nitrogen oxides (NOx): Similarly, nitrogen oxides can be released in small amounts.

However, carbon dioxide is the primary gas produced by the reaction between acid rain and limestone.