Official Explanation

This is a weaken question. Here are the conclusion and premise:

Premise: Mercy Hospital is being forced to eliminate 10 percent of its x-ray technicians and needs to preserve its standards of expert care

Conclusion: The technicians who take the longest time, on average, to fulfill their duties will be the ones let go.

This argument assumes that the technicians who take the longest to do their jobs are not the ones preserving the hospital’s standards of expert care. You want to weaken this question, so the right answer will attack this assumption.

Choice B does this by showing that the most difficult jobs, which take the longest to complete, go to the best technicians. The other choices do not attack the link between the technicians to be let go and the expert standards of the hospital.

Answer: B.