Since Professor Smythe has been head of the department, the most

very easy one
Imo C
Rest all options are not relevant

Can someone explain option B?
I selected C because it was the same thing that the conclusion is trying to state but option B also looks fine.

Following Nightblade354 advise to push my CR skills beyond the limits, I'll post an extensive analysis of this question, explaining the initial thoughts on the stimulus and the reasons why I reject four options and choose one as the winner . I beieve this is one of the best ways to improve in CR. Don't just do questions, but try to extract as much as possible from each of them. I think doing blind review help a lot in doing so (more about blind review here: https://gmatclub.com/forum/mod-nightbla%20...%2095316.html)

Here is the stimulus: Astrophysicist: Since Professor Smythe has been head of the department, the most distinguished member of the faculty has resigned, fewer new courses have been developed, student has dropped, and the reputation of the department has gone down. These facts provide conclusive evidence that Professor Smythe was appointed to undermine the department.

We want to see a flaw in the argument. Great. Have in mind all the common flaws described in Powerscore CR when reading the stimulus (Fallacies, survey flaw, cause-effect, errors in the use of evidence, errors in condtional reasoning, circular reasoning, errors of composition and division, etc)

1º premise: new head of department (cause?)
2º premise: a resignation, fewer new courses, #students dropped, lower reputation (effects?)
Conclusion: The cause leads to the effects

So it is easy to point out that this a cause and effect questions and the flaw might be related with this. Is the cause the reason to the effects? Is there any alternate cause that causes the effects? Look for something along these lines

(A) overlooks the fact that something can have the reputation for being of poor quality without being of poor quality

How do you know reputation is actually of non poor quality? and who said reputation is of poor quality? Stimulus says that reputation has gone down, but it could be that reputation's quality is not poor yet. In adittion, this doesn't align with what I was looking for. Incorrect

(B) bases a general claim on a few exceptional instances.

Ok. I like this one. It says that the claim (the head of department change is the only reason for the effects) is actually based on a few expectional instances. So it is recognizing that the effects could be exceptional and therefore the cause could not lead to the effects. Keep this one

(C) assumes that because an action was followed by a change, the action was undertaken to bring about that change

This is similar to B), so let's compare them. Option B talks about a general claim. which actually sounded a bit weird to me. General claim? I think general claims are made by a group of people (scientists, etc) and not just an author. I think this is what makes me choose Option C) over option B). So yes. Let's keep this one down

(D) fails to distinguish between a decline in quantity and a decline in quality

reputation is a decline in quality. So it considers both, quantity and quality. In addition, It has nothin to do with my initial thought. Incorrect

(E) presupposes what it purports to establish

It doesn't actually. It provides a cause/effect relationship and concludes that the cause leads to the effects. Incorrect

OPTION C