Corals live near the ocean surface in some warm regions of the world. the corals provide a home for algae. the algae, in turn, produce food chat is used by the corals. which of these is a biotic factor in this ecosystem?
a.. the temperature of the water
b. the salt content of the water
c. the size of the algae population .
d. the amount of sunlight that reaches the coral

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.

b. read the phase at the intersection of any given temperature and pressure.