Select from the following.
(a). roots
(b). rocks
(c). soil
(d). nitrogen
(e). ocean
(f). Carbon
(g). Crops
(h). well
Given those answer options, answer the question: Fact 1: Earthworm burrows help aerate soil, which is also good for plants. Fact 2: Insects and earthworms are very important in mixing and aerating the soil. Given the two facts above, what do earthworms mix?
A:
(c).