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.