The main thrust of this hunter's argument is that black bears have also played an important role in the decline of the deer population.

The evidence given for this argument:
- the forest's protected black bear population has risen sharply
- examination of black bears found dead in the forest during the deer hunting season showed that a number of them had recently fed on deer.

Thus, the first line that "Many people blame hunters alone for the decline in Greenrock National Forest's deer population over the past ten years" is the opposing viewpoint, and the one that the hunter seeks to refute.

(A) It is the main conclusion of the argument.
No, it is the opposing conclusion. The hunter's conclusion is that black bears are also responsible.

(B) It is a finding that the argument seeks to explain.
It's not a finding - it's an opinion.

(C) It is an explanation that the argument concludes is correct.
No - the hunter opposes this viewpoint.

(D) It provides evidence in support of the main conclusion of the argument.
It's not evidence - it's an opinion, and it's one that the argument rejects.

(E) It introduces a judgment that the argument opposes
Correct - it's the opposing viewpoint that the author argues against.

The answer is E.