Sentence Correction

Some anthropologists regard the early hominids' manner of walking (as being less efficient than in) modern human beings.

A. ()
B. as less efficient than it is in
C. as less efficient than that of
D. To be less efficient that that of
E. To have been less efficient than it is in


I don't understand why can't be option C....
Does "regard" need an infinitive? Regard (...) to be?
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I would go with E. I look at the meaning of the sentence. It is comparing the 'style of walking' of early hominids with modern man.

I would go with D on this. E seems wordy.

Not sure tho.

What is the OA?

I will pick D. What is OA ?

regard as is the correct idiom....and the style of walking shld be compared to that in human beings.......i think A is the ans