The answer is A.
The answer is A because that is the only positive of the entire set of answers.
B has a negative word of pollution which is something we are currently trying to stop.
C has threaten which would make other fish populations threatened or other aqua culture
And D has diseases which is obviously negative for the fact that diseases causes death and will ultimately lead to an endangered or extinct species if mutations or adaptions are not made.
Hope this helps!
