Pt 38, sec 2, q 6

[hotshot]

Ok so I've been sitting here trying to tackle this question but I was wondering if someone could explain why the answer is E. According to Kaplan it says that the other choices are possible but choice E is definitive. The question I have is, when working through this problem and coming across the answer choices that are possible, why would assume they're also not definitive. In other words, why should I have picked choice E, even though answers ABCD may also fit the criteria.

Any help is appreciated.