section 20 17

In the 1980’s the rate of increase of the minority population of the United States was nearly twice as fast as the 1970’s.

(A) twice as fast as

(B) twice as fast as it was in

(C) twice what it was in

(D) two times faster than that of（C）

(E) two times greater than

it 在这里就没有指代的歧义么？是不是因为前面的其它名词都是在of结构里呢？