This question is asking for you to find the flaw in the argument provided. The best way to go about this type of question is to break down the argument in your head. Here we have:
Premise: Income from sales of shirts and memorabilia is the same as at other concert series. Conclusion: The concert series has popular appeal.
So, the concert promoter is saying his concert series is popular because it sells the same amount of shirts/memorabilia as other similar concerts.
The flaw here is that we don't know how popular those other concerts are. They could all be horrible concerts that no one attends. If that were the case, their sales of shirts/memorabilia would likely be very low and could indicate an unpopular concert series.
Answer choices: (A) is incorrect. There is no discussion of emotions or emotional considerations.
(B) is incorrect. The argument does not claim that the sale of merchandise is the sole indicator of popularity, but rather that it is a good indicator of popularity. Thus, this answer choice is too strong.
(C) is correct. As described above, we don't know anything about these other concert series. The promoter is making an assumption about their popularity, but we have no evidence that they are popular.
(D) is incorrect. This answer choice is tricky. The key is that we actually know from the stimulus that these concerts are "similar." The answer choice states that they are dissimilar, and is therefore incorrect.
(E) is incorrect. The promoter is talking about series, not individual concerts. There is no need to make this distinction.