Linda wrote a few steps to describe how carbon circulates between the atmosphere and living organisms. Step 3 is missing.

Step 1: Carbon enters the atmosphere as carbon dioxide from respiration and combustion
Step 2: Plants use carbon dioxide to make glucose
Step 3:
Step 4: Animals exhale carbon dioxide

Which of the following best describes step 3?

a. Dead animals are buried underground and form fossil fuels.

b. Carbon present in glucose is converted into oxygen by animals.

c. Carbon present in glucose is transferred into plant-eating animals.

d. Dead animals decompose and recycle the carbon in the form of carbon dioxide.