C
Below is a question with multiple-choice answers. Choose the correct option based on your reasoning.

### Question:
Earthworms move randomly throughout topsoil. How do earthworms most likely affect the topsoil?

### Choices:
A. by compacting the topsoil
B. by decreasing the fertility of the topsoil
C. by adding nutrients to the topsoil
D. by removing the minerals from the topsoil

### Answer:
