Bunuel
The personal reminiscences of many personal acquaintances and business associates support the notion of there being many women who were significant figures in Andrew Carnegie's formative years.
(A) of there being many women who were significant figures
(B) of there being many women who significantly figured
(C) of many women who significantly figured
(D) that there were many women who significantly figured
(E) that there were many women of figurative significance
OFFICIAL EXPLANATION
D
First, you can assume that (A) and (B) are almost certainly wrong, due to the phrase "of there being". "Being" is almost always incorrect. (E) also has a major flaw: "figurative significance" means something very different from "significantly figured".
The key difference between (C) and (D) is "of" versus "that there were". While "of" is shorter, whatever follows a phrase like "support the notion" must be a complete sentence. (D) connects "the notion" to the complete sentence starting with "there were many women. . ." with the word "that". (C) does not, so (D) is correct.