A River Is Flowing in a Broad,alluvial Valley and the River

Multiple Choice

A river is flowing in a broad,alluvial valley and the river is silt-laden but also moves sand and a small amount of gravel.The government decides to build a dam across the valley for power and flood control.What will happen to the river,upstream of the dam?

A) The river will downcut.
B) The river will start to deposit sand and gravel,frequently spilling out of its channel.
C) The river will not change.
D) The river will respond to the new temporary base level and cut laterally outside its valley,widening the valley.