You are presented with the question "What do earthworms mix?" and the following answer choices: 
- roots
 - rocks
 - soil
 - nitrogen
 - ocean
 - Carbon
 - Crops
 - well

Now knowing that earthworm burrows help aerate soil, which is also good for plants and insects and earthworms are very important in mixing and aerating the soil, choose the best answer.


 

   soil      