Answer:
The correct answer is C. the size of the algae population .
Explanation:
An ecosystem is made up of biotic and abiotic factors. Biotic factors are the living components of an ecosystem that impact the ecosystem and abiotic factors are the non- living components that have their own impact on the ecosystem.
So according to the definition of biotic factor algae is the biotic factor in this question because algae is a living component of the ecosystem that influences the ecosystem by providing food to the corals.
So by providing food algae supports the coral's ecosystem and coral provides a home to algae to grow. In the ecosystem, both biotic and abiotic factors interact with each other.
So the correct answer is C. the size of the algae population.