The answer is D, algae.
—Evidence—
•] Protozoan definition: a single-celled microscopic animal of a group of phyla of the kingdom Protista, such as an amoeba, flagellate, ciliate, or sporozoan.
•] it does not feature algae, therefore it’s D.
Temperature is considered an biotic limiting factor. The correct answer is A.
The answer is D. All of the choices pertain to living organisms