Answer:
We can immediately cross-out C
We can also cross-out A.
Now we have B and D. Commensalism and Mutualism. Now, commensalism is an association between two organisms in which one benefits and the other derives neither benefit nor harm.
Mutualism is the doctrine that mutual dependence is necessary to social well-being.
I would say D: Commensalism. Both fish can survive without each other.
