I'm going with
C here.
We are first provided the information that towns Y and Y are very similar in size and population, making them comparable. Then, we find out that in the months of June & July, Y had double the car accidents that X did. The conclusion here is that
if the car repair franchise were looking to open a new shop in one of the two towns, it would be more likely to succeed in Town Y. The reason for this? Double the car accidents = double to work for the franchise. BUT, our job is to attack this conclusion, aka choose an answer that logically explains why this is a bad idea.
A) That's great but the statement that there have been double the car accidents in June and July still stands! Nothing here that explains this.
B) If anything, this would possibly strengthen the conclusion, not weaken
C) CORRECT Y is a beach town, i.e., there are a lot more people (tourists) that travel there and thus, the franchise for car repair would only have this increased workload during those Summer months. Since we don't know what the number of car accidents for Y is during the remaining months, there is no proof that the franchise would be more successful there than in town X
D) 6 years ago is just out of scope - not relevant today
E) a megamall would mean more people but we are not allowed to just assume that this would automatically lead to more car accidents.