Sentence Correction

813). The question of whether to divest themselves of stock in companies that do business in South Africa is particularly troublesome for the nation’s 116 private Black colleges because their economic bases are often more fragile than most predominantly White colleges.
(A) than

(B) than those of

(C) than is so of

(D) compared to

(E) compared to those of

Why is C preferred as compared to E

Is it that in E- "as" is missing