erosion of cliffs. water flowing into a lake. dams being built by beavers. sediment being moved downstream by water.
I gave my students this multiple choice question: Sandbars form in many rivers because of

Only one answer is correct among these 4 choices:
- erosion of cliffs.
- water flowing into a lake.
- dams being built by beavers.
- sediment being moved downstream by water.

Could you tell me which one is correct?

sediment being moved downstream by water.