Currents prevent accumulation of most organic matter .
Option C
Explanation:
The fast flowing water in the river will always have a current which if formed due to flow pattern and channel geometry. Normally if the river water is flowing from a high point then there will be current; this will be associated with the volume of water flow.
The flowing water always displaces the soil which has organic matter from one place to another. In the fast flowing water the underwater current will push the rock and mud at a very great speed and prevent the accumulation of soil in one particular place.