How will the right answer fit in terms of support and conclusion?

Only the right answer will support the conclusion in the prompt that the “actions would be unethical”.

Highlight the main conclusion in the passage, if there is one:

The passage is just a “principle”, or general rule. There is no conclusion in this passage.

[SUPPORT].

Map the wording of the answers to the wording of the passage:

(A) …was one of several bidders…

We don’t see anyone actually “financially benefit” in this one.

(B) …He uses his contacts with department officials…

Careful, it doesn’t actually say he’s using “knowledge of impending policies”. He could just be networking. So this doesn’t really map to the wording of the principle.

(C) …that were allowed by the new law.

Sounds like this is happening after the law is in effect, so the official isn’t using “knowledge of impending policies”.

(D) …before the plan was announced to the public in order to avoid paying…

That says it all. A “plan to tax luxury cars” maps to “impending policies”, and avoiding taxes clearly means the official “financially benefit themselves”.

(E) …just after she announced…

So there’s no “impending policies” in this one either.

(D) is the correct answer.