题目选项分析

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?

【选项】The first provides support for main conclusion of the argument; the second calls that conclusion into question.