B. Segregation.
I have the same question and answered it and this is what it told me. I think it should be right.
Answer:
C
Explanation:
because there is not enough surface area to grow more
The barnacles are only able to attach them selfs to surfaces in the water. Since the surface is limited, barnacles are attaching themselves to the other barnacles, crowding the rock. The muscles were not able to grow or attach themselves off the surface of the rock. Same thing with the mussels that are growing on the rock. So not only barnacles are crowding the rock, but Mussels as well are crowding the rock.
Description 2 describes a commensal symbiosis. The answer is D, commensalism.
