Much of the action is in the non-underlined portion of this sentence: “Almost like clones in their similarity to one another...” That phrase includes the plural pronoun “their”, so it needs to be followed by a plural noun that could reasonably be described as “like clones” in terms of their similarity to each other.
With that in mind…
Quote:
(A) the cheetah species’ homogeneity makes them especially vulnerable to disease
(A) definitely doesn’t work, because “the cheetah species’ homogeneity” is singular, and it’s unreasonable to say that the “homogeneity” is “almost like clones in their similarity to one another.”
So (A) is out.
Quote:
(B) the cheetah species is especially vulnerable to disease because of its homogeneity
The trouble here is that “the cheetah species” is singular, and once again, a singular species can’t logically be described as “almost like clones in
their similarity to one another.” (And in case you’re wondering: yes, “species” can also be plural, but in this case, it’s followed by “is”, and then “its” refers back to “species” later in the sentence. So “species” is definitely singular in this particular sentence.)
We can eliminate (B), too.
Quote:
(C) the homogeneity of the cheetah species makes it especially vulnerable to disease
(C) repeats the exact same error as (A): “the homogeneity” is singular, and it’s still totally unreasonable to say that the “homogeneity” is “almost like clones in their similarity to one another.”
That takes care of (C).
Quote:
(D) homogeneity makes members of the cheetah species especially vulnerable to disease
(D) rearranges a few things, but the heart of the problem is still completely the same as in (A) and (C): “homogeneity” is singular, and it’s once again unreasonable to say that the “homogeneity” is “almost like clones in their similarity to one another.”
(D) is gone, and I really hope we like (E), or else we’ll be starting over…
Quote:
(E) members of the cheetah species are especially vulnerable to disease because of their homogeneity
Yup, this is fine! “Members” is plural, and it makes sense to say that “members of the cheetah species” are “almost like clones in their similarity to one another.”
“Their” also jumps out at me at the end of the sentence, and that’s fine, too: “their” refers to “members of the cheetah species.”
So (E) is our winner.