再问twice what it was in???

4.         A survey by the National Council of Churches showed that in 1986 there were 20,736 female ministers, almost 9 percent of the nation's clergy, twice as much
                            as 1977.

A.twice as much as 1977 B.twice as many as 1977 C.double what it was in 1977

D. double the figure for 1977

E.a number double that of 1977's

D Correct. Double the figure places the emphasis

of the sentence on the number of ministers; for

1977 correctly completes the comparison.

但对于下面885中的一题:
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
(E) two times greater than
答案C.

为什么2个题里面其中一个的解释是what it was是awkward?而在另外一个里面又是答案?难道仅仅是因为twice 和double的用法区别还是因为别的?

另外请教increase的用法 72. The number of undergraduate degrees in engineering awarded by colleges and universities in the United States increased by more than twice from 1978 to 1985.
(A) increased by more than twice
(B) increased more than two times
(C) more than doubled
(D) was more than doubled
(E) had more than doubled

答案是c 请问 b 和d为什么错了. 问题比较多 请大家耐心讨论.