deposition weathering precipitation photosynthesis
I gave my students this multiple choice question: The iron in iron-rich red soils may not be in a form that can be taken up by tree roots. As a result, leaves and needles may look yellow. Some trees release acids that convert iron in soil to a usable form. This change in soil chemistry is a type of which process?

Only one answer is correct among these 4 choices:
- deposition
- weathering
- precipitation
- photosynthesis

Could you tell me which one is correct?

weathering