GMAT Sentence Correction (SC) | Re: The managers were asked to rate their depth

The managers were asked to rate their depth of knowledge having been increased as a result of the emergency simulation, and in each area, they reported large gains

(A) their depth of knowledge having beenincreased
having being increased is incorrectly used to explain the intended meaning of the sentence
(B) how much their depth of knowledge had increased
this option clears the intended meaning of the choice. Must be the correct choice (C) if they had more knowledge
Plural subject "they" must
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