Question

marine snow is _________.
a. pieces of organic matter that were once part of living organisms
b. a mixture of living plankton
c. snow from land that has entered aquatic ecosystems
d. large salt crystals that have not dissolved in ocean water

Explanation:

Marine snow consists of organic matter (like dead plankton, feces, etc.) that was once part of living organisms. It is not living plankton (so b is wrong), not land - based snow (so c is wrong), and not salt crystals (so d is wrong).

Answer:

A. pieces of organic matter that were once part of living organisms