If Erosion and Deposition Occur at the Same Rate,how Can

If erosion and deposition occur at the same rate,how can we best describe the particles of sediment on a streambed?

A) Only very small particles will be present along the stream bottom.
B) Particles neither move in,nor move out of this part of the stream.
C) As the sediment moves downstream,it is replaced by a similar volume of sediment.
D) Pebbles and cobbles carried away are replaced by the same number of smaller particles.