The correct answer is option 2: Hydration.

Hydration refers to the process of certain minerals absorbing water molecules into their crystal structure. This absorption causes expansion and puts additional stress on the surrounding rock.

Option 1, Hydrolysis, is not the correct answer. Hydrolysis is a chemical reaction where water breaks down other compounds, but it does not directly cause the expansion of minerals in the rock.

Option 3, Oxidation, is also not the correct answer. Oxidation is a reaction where a substance combines with oxygen, and while it can lead to the deterioration of minerals in the rock, it does not specifically cause the expansion of minerals.

Option 4, Carbonation, is not the correct answer either. Carbonation is a process where carbon dioxide reacts with water to form carbonic acid, which can dissolve minerals in the rock. However, it does not directly cause the expansion of minerals either.

Therefore, the correct answer is option 2: Hydration.