<p>I have discovered that the subways in New York are [as clean as any other city I have visited.]
A. as clean as any other city I have visited
B. as clean as those in any other city I have visited
C. as clean as those in any city I visited
D. cleaner than any city I visited
E. cleaner than any other city I have visited.</p>
<p>because in c, you're also saying "I have discovered that the subways in New York are as clean as those in New York." without the other, you include NY as well, which makes a ridiculous comparison. it's definitely b</p>
<p>That is a reason why C isn't correct. If you remove "other" than you are not distinguishing other cities from New York, and you are in fact including it in the list of cities who are assumed to not be as clean. If possible, when correcting sentences, you don't want to remove too many words from the sentence unless absolutely necessary. Although removing words may make the sentence shorter, it often takes away from the original idea/point that the sentence is trying to make.</p>