Seems A to me

what is the mistake with B.

what is the mistake in B.

Both A & B look fine to me.

In B, "likely severely disadvantaged" is awkward.

Chitturi wrote:what is the mistake in B.

Both A & B look fine to me.

A vertical scan reveals three basic issues:
(i) "likely" versus "liable"
(ii) "at a severe disadvantage" versus "severely disadvantaged"
(iii) "often unable to" versus "cannot often" versus "unable that it can". We will address these issues one at a time.

On the GMAT, "liable to" is acceptable when followed by a negative possibility; therefore, we cannot use this issue to eliminate answers here.

The word "disadvantaged" is typically used in a socio-economic context; therefore, its use here is questionable. That makes (B) and (C) questionable, but since the word "disadvantaged" is not outright wrong, let's examine the third issue before eliminating answers.

"Unable that it can" is idiomatically incorrect so we eliminate (E). "Cannot often" implies that every orphaned bull moose is unable to protect itself against frequent attacks by predators. While this may be true, this changes the meaning of the original sentence. In the original sentence, "often unable to" implies that many orphaned bull moose are not able to protect themselves against predators. Thus we eliminate (C) and (D).

That leaves (A) and (B). Based on the above discussion of "disadvantaged" versus " at a . . . disadvantage", we eliminate (B), and (A) is our best answer. OA A