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

The answer is C. Why? "it" refers what in C?

"it" refers to the rate of increase of the minority population of the

United States,

如果觉得it的指代不够合理，那么其余任何一个选项都有极为明显的错误。