That Of vs Those Of

I have some confusion regarding the use of "that of" & "those of"

Now I was told that the only difference is that "that of" is to refer to singular nouns & "those of" is used to refer to plural nouns.

eg: Analysts wonder whether the future of the Blue Oval is much different from that of General Motors Corp. and Chrysler LLC

that of -> future of

But in another question

Unlike most warbler species, the male and female blue-winged warbler are very difficult to tell apart.

(A) Unlike most warbler species, the male and female blue-winged warbler are very difficult to tell apart.

(B) Unlike most warbler species, the gender of the blue-winged warbler is very difficult to distinguish.

(C) Unlike those in most warbler species, the male and female blue-winged warblers are very difficult to distinguish.

(D) It is very difficult, unlike in most warbler species, to tell the male and female blue-winged warbler apart.

(E) Blue-winged warblers are unlike most species of warbler in that it is very difficult to tell the male and female apart.

GMAT Ninja commented on this question and said -


Now I'm really not sure what is correct or is it that "that of" can refer to the head noun and "those of" cannot?

GMATNinja KarishmaB AndrewN AjiteshArun MartyTargetTestPrep

Thanks

-Aum