In the Cheseapeake Bay ecosystem, beds of eelgrass provide food and shelter to growing blue crabs. As blue crabs mature, they feed on fish and are fed on by larger animals like egrets. As organisms die, decomposers like bacteria in the sand of eelgrass beds help break down organic material.

Which of the following correctly matches a biotic factor in this ecosystem to the role it plays in cycling matter?
A.
Decomposers release carbon dioxide that eelgrass use for photosynthesis.
B.
Blue crabs convert carbon dioxide to organic sugars through respiration.
C.
Fish and other animals convert nitrogen to a form that can be used by plants.
D.
Sand contains nutrients like nitrogen that it transmits to eelgrass.