Question

3.a.2 test (cst): computer-scored unit test
a. oxygen
b. hydrogen
c. nitrogen
d. carbon
(diagram labels: cellular respiration, photosynthesis, fossil fuels, animals, plants, industry and homes, death and decay)

Explanation:

The diagram shows processes like photosynthesis, cellular respiration, and the role of fossil fuels and decay. Photosynthesis takes in carbon dioxide (containing carbon), cellular respiration releases carbon dioxide, fossil fuels (formed from dead organisms) when burned release carbon - based compounds, and death/decay also involve carbon cycling. Oxygen, hydrogen, and nitrogen cycles don't match this diagram's processes as closely as the carbon cycle.

Answer:

D. Carbon