Critical Reasoning

A very similar question but with different patterns, https://gmatclub.com/forum/after-the-re ... 74927.html
After the recent court rulings, commercial shark fishing and shark hunting will resume in Diamond Bay. Many citizens of the communities around the bay have hailed this move, believing that a decrease in sharks will lead to an increase in all smaller fish, including the endangered Green-Gilled Silverfish, whose only ecosystem is within Diamond Bay. Ecologists, though, disagree, pointing out that a decrease in sharks will lead to a surge in Sea Lions, which are the principal predator of the Green-Gilled Silverfish.

In the argument given, the two portions in boldface play which of the following roles?

A The first provides support for main conclusion of the argument; the second calls that conclusion into question.
B The first describes evidence that has been taken as supporting a conclusion; the second states a contrary conclusion C that is the main conclusion of the argument.
C The first is an opinion that the argument opposes; the second is evidence inconsistent with the conclusion of the argument.
D The first is a conclusion that the argument as a whole seeks to justify; the second is an explanation that supports this conclusion.
E The first supports an action as a beneficial; the second calls that evaluation into question.

What's the best approach to determine the answer? Can any experts show?