Pankaj1Agarwal
The truth is that (A) is debatably correct.
In any well-written official question, the incorrect answers clearly have the wrong effect. For instance, an incorrect answer to an Assumption question may actually weaken the argument or may support the wrong conclusion.
Choice (A), on the other hand, does not clearly have the wrong effect. If we assume that losing employees would be detrimental to the performance of a company, which assumption is not exactly a huge leap, then (A) does state an assumption necessary for going from the evidence presented to the conclusion that changing the policy will have a positive effect on company performance.
On the other hand, the conclusion is specifically about the effects of the "resulting decrease in absenteeism," while (A) is about effects of losing employees. So, perhaps one could make the case that (A) is not necessary for arriving at a conclusion about the effects of a decrease in absenteeism.
Regarding (C), (C) does seem to apply directly to the conclusion. However, because of the way in which the argument is written, it's not clear whether "the resulting decrease in absenteeism" is basically a premise, or the conclusion is that a decrease in absenteeism will result.
So, (C) is not 100 percent clearly correct either.
The upshot of all of the above is that this question is not particularly well written, and, as a result, there is no great way to eliminate choice (A) or make a flawless case for choosing choice (C).
I think one could get this question "correct," if there is such a thing in this case, by figuring out that the conclusion is really supposed to be that absenteeism will decrease and that, therefore, (C) is a cute answer that states an assumption necessary for arriving at that conclusion. However, really, this question is rather flawed and has two potentially correct answer, and therefore, what you would have to do in order to arrive at the OA is not really representative of what you need learn to do in order correctly answer GMAT Critical Reasoning questions.