Please help
What is the type of reaction and why do you think that

most sediment washes or falls into the river as a result of mass movement and runoff. other sediment eroded from the bottom or sides of the river.

i believe it is c.) 1575 j.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).