In the consultant's reasoning, the two portions in boldface play which of the following roles?
Conclusion of passage: The 2nd attempts at repairs jobs are better because of level of concentration of mechanics and not due to their incompetence.
first- finding. second- its explanation

A. The first is the consultant's main conclusion; the second provides evidence in support of that main conclusion.
incorrect. main conclusion is something else.
B. The first is evidence that serves as the basis for rejecting one explanation of a certain finding; the second is the consultant's own explanation of that finding.
incorrect- first one is not evidence rather a finding.

C. The first is a claim whose truth is at issue in the reasoning; the second provides evidence to show that the claim is true.
incorect- first one is not a claim but finding.
D. The first presents a contrast whose explanation is at issue in the reasoning; the second is the consultant's explanation of that contrast.
correct- First one is finding which reveals a contrast.
E. The first presents a contrast whose explanation is at issue in the reasoning; the second is evidence that has been used to challenge the consultant's explanation of that contrast.
incorrect- the second one is not used to challenge the consultant's explanation.