"As...as" is the proper construct to employ when comparing items that are equal in some sense, therefore using "as" in this context is inappropriate (which is what happens in the sentence) So, the correct response is D.
Choice (A) uses awkward wording. As demands "such" come before it. Option (B) uses awkward wording. Should read "such as," not "that are." An incorrect idiom is present in Option (C).
It should be "diversity such as," not "such diversity." There is an agreement issue with Option (E) (in number). The varioussubjects mentioned cannot be referred to as "a subject".