Critics of the research study claimed that monkeys are different enough from human beings that comparing the two species can be as questionable—or as useless—as comparisons between humans and mice.

(A) different enough from human beings that comparing the two species can

(B) different enough from human beings so that comparing the two species can

(C) different enough from human beings for comparing the two species to

(D) so different from human beings that comparisons between the two species can

(E) so different from human beings for comparisons between the two species to

So X that Y is correct idiomatic usage , hence the correct answer must be (D)
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