When sediment is transported down a mountain and along a stream, we are seeing the conservation of

D.matter

Explanation:

As the sediments are transported downwards by the stream with the force of gravity they are then transported to the base of the river or the slope and this downwards transportation and flow of sediments are related to the conservation of matter. Where the mass of matter sediments remains the same and thus the sediment quantity can be neither be created nor destroyed, the speed at which the sediment flow can be increased or decreased. It's the principle of the chemical changes that matter can be neither be created nor destroyed the flow of the energy is unidirectional.

Answersource rock;