Concept:Mechanical weathering is the physical breakdown of rocks without any change in their chemical composition.
Explanation:Temperature changes cause rocks to expand and contract, leading to cracking.
Frost action occurs when water freezes in cracks and expands, splitting the rock.
Alternate wetting and drying also weakens rock particles and causes breakdown.
Rain action is not a mechanical process because rainwater mainly reacts with rock minerals, making it a chemical weathering process.
Therefore, the option that is not a cause of mechanical weathering is rain action.
Answer:D. rain action