A. Producer
B. Primary consumer
C. Secondary consumer
D. Tertiary consumer

I'm pretty sure it's B. Primary consumer.

Explanation:

The protozoa eats the algae, making it a primary consumer.

B

Explanation:The reason why the answer is a because that protozoa is mostly a decomposer by eats organic matter or debris.Also primary consumers are mostly described as primary consumers or in other cases it mostly depends on the food web it self.Hope it helps again!

c.more precipitation,but only when emission levels.