39. GWD21-Q39:

Almost like clones in their similarity to one another, the cheetah species’ homogeneity makes them especially vulnerable to disease.

A.      the cheetah species’ homogeneity makes them especially vulnerable to disease

B.      the cheetah species is especially vulnerable to disease because of its homogeneity

C.      the homogeneity of the cheetah species makes it especially vulnerable to disease

D.      homogeneity makes members of the cheetah species especially vulnerable to disease

E.       members of the cheetah species are especially vulnerable to disease because of their homogeneity

为什么选E?不选D?

3QQQ