How can organic matter in soil affect chemical weathering?

Correct answer: They can form acids that help dissolve minerals

The direct answer is A: organic matter can form organic acids that help dissolve or alter minerals. Soil contains humus made from decomposed plants and animals. During decomposition, some organic acids may develop. When water carries these acids into cracks and soil spaces, they can react with minerals in rocks and make chemical breakdown easier. Option A is correct because it explains the link between organic matter, acids and mineral dissolution. Option B is wrong because organic matter does not permanently remove all water; water is often needed for chemical weathering. Option C is wrong because organic matter does not make every rock hard. Option D is wrong because it does not fix temperature at zero; soil temperature changes with conditions. The effect depends on the material and environment, but the stated process is scientifically valid. Memory cue: humus plus acids can speed chemical weathering.