请教“倍数+名词的用法”的知识点

“404.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
(E) two times greater than
the key: C
比较考点：倍数+名词的用法”

对这种用法实在不解，请问有谁可以帮忙将解释一下，或者举个例子？^_^谢谢回复

这题主要考的还是比较结构。

关于倍数的用法置顶贴里有