Bunuel
The Sherpa people, indigenous to the mountainous regions of eastern Nepal, are known to have their ability of performing with ease the demanding tasks of mountaineering at some of the highest known altitudes.
A. to have their ability of performing with ease
B. to have the ability with their performing with ease
C. for their ability to perform with ease
D. for their ability of performing with ease
E. in the ability to easily perform
Magoosh Official Explanation:
The primarily idiom in this question concerns the word “ability”, which must take the infinitive. Only (C) and (E) have an infinitive, although (E) has a mistake known as the split infinitive: it inserts an adverb between the “to” and the verb of an infinitive. The split infinitive was once considered completely wrong. It is gaining acceptance in casual speech and pop culture (“To boldly go where no man has gone before“), but this will not be part of a correct answer on the GMAT Sentence Correction.
Also, notice the secondary idiom, “to be known for something.” That is the correct way to express this —- the Sherpa are known for their mountaineering skill. The other constructions (“known to have the ability”, “known in their ability”) are idiomatically incorrect ways to express this idea.
The best answer is (C).