Answer:
Explanation:
A biotic factor is a living thing in an ecosystem. For example: deer, rabbits, grass and trees are all biotic factors.
An abiotic factor is a nonliving thing in an ecosystem. Some examples include rocks, soil, and water.
Let's examine our answer choices.
Sunlight, nutrients, and precipitation are all nonliving, so they are abiotic factors. They can't be the correct choice.
That leaves: <u>microorganisms.</u> Microorganisms are very tiny organisms, like bacteria and amoebas. They are biotic factors, so the correct choice is D. microorganisms