The correct answer is option 1: Acid rain. `Stone Cancer` is a term used to describe the erosion and degradation of stone structures, such as buildings and statues, due to the effects of acid rain. Acid rain is formed when emissions from industries and vehicles, such as sulfur dioxide and nitrogen oxides, react with water vapor in the atmosphere. This forms sulfuric acid and nitric acid, which then falls back to the ground as acid rain. When acid rain comes into contact with stone surfaces, it slowly corrodes and damages the stone, leading to the deterioration and disintegration of the structures over time. The other options, global warming, radioactivity, and bacterial action, are not directly related to the occurrence of `Stone Cancer.`