I actually had a bit of a chuckle with this one! I guess too much GMAT has warped my sense of humor...

The problem in C and D is that - unlike E - there is no proper containment of the the "tourists." You see in answer choice E "exhaled by tourists" is a clear, limited modifier applying to moisture. Try reading the "because" clause without the modifier and it works "because moisture...had raised the humidity levels..."

In C and D, especially in C "tourists" is positioned in such a way that "tourists" is not clearly confined and cannot easily be lifted from the sentence. In fact, in C "tourists" is the subject of the because clause making it unclear whether the humidity was raised in the chambers or in the tourists (which is what I found humorous). D suffers from the same problem, the positioning of the -ing modifier could clearly signal that this modifier is applied to the previous word, "tourists."

I applaud your efforts to make sure you understand every possible angle, just remember, as a strategy, you always want to use your best decision point first. So if the other errors you talked about - parallelism and agreement - are working for you on this particular sentence use those first. On some other sentence you might need the ambiguity. You only have to eliminate wrong choices for one valid reason in order for "them" to be eliminated.

David@VeritasPrep wrote:I actually had a bit of a chuckle with this one! I guess too much GMAT has warped my sense of humor...

The problem in C and D is that - unlike E - there is no proper containment of the the "tourists." You see in answer choice E "exhaled by tourists" is a clear, limited modifier applying to moisture. Try reading the "because" clause without the modifier and it works "because moisture...had raised the humidity levels..."

In C and D, especially in C "tourists" is positioned in such a way that "tourists" is not clearly confined and cannot easily be lifted from the sentence. In fact, in C "tourists" is the subject of the because clause making it unclear whether the humidity was raised in the chambers or in the tourists (which is what I found humorous). D suffers from the same problem, the positioning of the -ing modifier could clearly signal that this modifier is applied to the previous word, "tourists."

I applaud your efforts to make sure you understand every possible angle, just remember, as a strategy, you always want to use your best decision point first. So if the other errors you talked about - parallelism and agreement - are working for you on this particular sentence use those first. On some other sentence you might need the ambiguity. You only have to eliminate wrong choices for one valid reason in order for "them" to be eliminated.

lol
Thank you David~