Critical Reasoning

You could make Sentence Correction questions out of most of the sentences above. For example:

"A marketing investigation shows that while more costly, tourists electing the "inexpensive" option ... "

Clearly the tourists are not 'more costly' than something else, which is what the sentence above says. I'm also not sure why 'percentages' is pluralized, since the answer is talking about one percentage only. I find the question so badly written that I can't understand what many of the sentences mean. Despite its grammatical issues, answer choice C seems to be saying that the inexpensive option is 'more costly' than the 'all included' option. Since that tells us exactly what we want to know, that would clearly strengthen the argument.

Answer choice B includes an incomplete comparison - "5% higher" than what? - and also seems to be saying that the 'payment' is 'charged individually', which makes no grammatical sense. So it's hard to guess just what answer choice B even means. I'm guessing it means that the total cost of one buffet and one scuba diving course is equal to 5% of the cost of the 'inexpensive' cruise itself. If that's what B is saying, it doesn't help much, since while we would then know that some of the 'extras' are expensive relative to the cost of the cruise, we have no information about the difference in the cost of an 'all-inclusive' and an 'inexpensive' cruise. So if B means what I'm guessing it means, it's certainly not a good answer here. If on the other hand, when they write "5% higher", they're comparing the cost of the inexpensive cruise with two extras to the cost of the all-inclusive cruise, then it is a somewhat good answer, since it would then tell us that even by buying just two extras a passenger will spend more on the "inexpensive" cruise. Still, it's not a great answer, because there remains the possibility that scuba diving is both an extremely expensive 'extra' and a very unpopular one. If most passengers don't take scuba diving, then the cost of a scuba diving 'extra' is not particularly relevant to the argument.

It's one of those questions that is so poorly written that you can't pick a good answer unless you can guess what the question designer was thinking, since the answer choices can be interpreted in different ways. I'd recommend just moving on to better-written questions and not worrying about this one, since you won't see something this convoluted on a real GMAT.