Answer:
Ok I need more of the question more info.
Explanation:
The lac repressor prevents the lac genes in the DNA of E. coli from being expressed most of the time. The answer to your question is A. I hope this is the answer that you are looking for and it comes to your help.
Well If the Salmon die from lack of food from polution or something, and other animals benafit from the nutrience they carry. the rest of the ecosystem might parish, i hope that helped im not sure what was wanted