Answer:
C. Carbon compounds
Step-by-step explanation:
The animals are living organisms, so they eventually die. As they die, their bodies start to fall apart in a process known as decomposition. This process is caused by the microbes. As the bodies of the animals are decomposing, multiple compounds are released into the soil. One of the those compounds are the carbon compounds. The animals are natural storage of carbon because throughout their lives they consume it through their food, so parts of it are retained into their bodies.