What is/are one source of mineral deposits on the seafloor?

A. Coral reefs

B. Lagoons

C. Seafloor spreading

D. Volcanic vents

Answer: D. Volcanic vents

Volcanic vents are one source of mineral deposits on the seafloor.

Explanation:

Volcanic vents are openings which are exposed on the earth's surface where volcanic material is discharged or emitted. They originated in the magma chamber which is an underground pool of liquefied rock located underneath the surface of the Earth. They can be found at the on the flanks of a volcano or at the summit of a volcano. It is a source of mineral deposits on the seafloor.

I believe D is the answer ...