The gas produced when acid rain falls on a limestone statue is carbon dioxide (CO2).

Here's why:

* Limestone is primarily composed of calcium carbonate (CaCO3).

* Acid rain contains sulfuric acid (H2SO4) and nitric acid (HNO3).

* When these acids react with calcium carbonate, they form calcium sulfate (CaSO4), calcium nitrate (Ca(NO3)2), and carbon dioxide (CO2).

The reaction can be represented by the following simplified equation:

CaCO3 + H2SO4 → CaSO4 + H2O + CO2

This reaction is responsible for the erosion and damage of limestone statues caused by acid rain.