Here's a problem to solve: Earthworms move randomly throughout topsoil. How do earthworms most likely affect the topsoil?

Among the 4 following options, which is the correct answer?

- 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
 