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?

  Options: 
 A. deposition
 B. weathering
 C. precipitation
 D. photosynthesis
Answer: B