erosion fertilizer chemical weathering mechanical weathering
I gave my students this multiple choice question: Lichens grow on rocks and produce an acid that reacts with part of the rock, forming soil. Which best describes the action of lichens on the rocks?

Only one answer is correct among these 4 choices:
- erosion
- fertilizer
- chemical weathering
- mechanical weathering

Could you tell me which one is correct?

chemical weathering