water freezing in cracks of rocks glaciers carving out a valley river water eroding the banks of a stream bacteria breaking down dead matter
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which process will directly result in organic matter being added to the soil?
Possibilities:
- water freezing in cracks of rocks
- glaciers carving out a valley
- river water eroding the banks of a stream
- bacteria breaking down dead matter

bacteria breaking down dead matter