An intertidal species of seastar helps to maintain the diversity of the intertidal region by controlling the mussel population. Without the seastar, the mussel population would crowd out other species and take over their territory. The seastar could be called a(n)

a. indicator species
b. keystone species
c. foundation species
d. aggressive species
e. repressor species

b. keystone species

Explanation:

The keystone species is the species which exerts an effect on the communities in which they grow. Such species helps in maintaining the diversity of local animal species.

The keystone species is the dominant predator species. It controls the population of the predator species.  

According to the given situation, the seastar is the dominant predator species which is capable of controlling the population of the mussel species. Hence, the seastar could be a keystone species.

a

explanation:

because it is and it's just life man

i am going to guess that it is co2.