A Stream Channel is formed when water

{A. carves a narrow path into rock.}

B. carries minerals into the ocean.

C. carves a very deep and wide channel into rock.

D. creates a depression, which forms a lake.

It's a difficult question to answer. A stream channel is the physical confine of a river, and consists of a bed and stream banks, but also the path of water and sediment flowing within the stream banks.

Considering this info, and since we don't have any other clue about the mass of water we're talking about, I'd go for the B, is formed when water carries minerals into the ocean.