The ultimate source of most of the material found on the surface of abyssal plains is

Question

A sediments carried to the ocean by continental rivers.

B shells settling from the ocean surface.

C sediments eroded from abyssal hills.

D sediments produced at mid-ocean ridges.

Answer 1

C sediments eroded from abyssal hills.  Sediments from continental rivers, never reach the abyssal plains.

Answer 2

The ultimate source is A.. The continents are the great source for materials that cover the abyssal plains.  Erosion of the land and the transportation of the eroded material by rivers to the oceans produce the material that eventually falls to the bottom of the sea.  Only a small fraction of this material reaches out into the ocean basins where the abyssal plains are located.  Thus, many thousands of years are required to produce a few inches of this seabed.