Anatomical bilateral symmetry is a common trait. It follows, therefore, that it confers survival advantages on organisms. After all, if bilateral symmetry did not confer such advantages, it would not be common.

The pattern of reasoning in which one of the following arguments is most similar to that in the argument above?
(A) Since it is Sawyer who is negotiating for the city government, it must be true that the city takes the matter seriously. After all, if Sawyer had not been available, the city would have insisted that the negotiations be deferred.
(B) Clearly, no candidate is better qualified for the job than Trumbull. In fact, even to suggest that there might be a more highly qualified candidate seems absurd to those who have seen Trumbull at work.
(C) If Powell lacked superior negotiating skills, she would not have been appointed arbitrator in this case. As everyone knows, she is the appointed arbitrator, so her negotiating skills are, detractors notwithstanding, bound to be superior.
(D) Since Varga was away on vacation at the time, it must have been Rivers who conducted the secret negotiations. Any other scenario makes little sense, for Rivers never does the negotiating unless Varga is unavailable.
(E) If Wong is appointed arbitrator, a decision will be reached promptly. Since it would be absurd to appoint anyone other than Wong as arbitrator, a prompt decision can reasonably be expected.

lost on this one

C for me

Anatomical bilateral symmetry is a common trait = X
It confers survival advantages on organisms = Y
If bilateral symmetry did not confer such advantages = If not Y
It would not be common = not X

X -> Y
not Y -> not X

(C)

She is the appointed arbitrator = X
so her negotiating skills are bound to be superior = Y
If Powell lacked superior negotiating skills = If not Y
She would have been appointed arbitrator in this case = not X

X -> Y
not Y -> not X
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Auge um Auge, Zahn um Zahn !

formulating the logic as gamjatang did, I also get C.