cause disease in living organisms. reduce soil erosion. recycle oxygen to the air. return nutrients to the soil.
I gave my students this multiple choice question: Decaying plants and animals are important to an ecosystem because they

Only one answer is correct among these 4 choices:
- cause disease in living organisms.
- reduce soil erosion.
- recycle oxygen to the air.
- return nutrients to the soil.

Could you tell me which one is correct?

return nutrients to the soil.