老prep2-32题求助！

蕾咪

32. (26170-!-item-!-188;#058&003042)

The Chicago and Calumet

Riversoriginally flowed into the St. Lawrence by way of Lake Michigan, but havingbeen redirected by constructing canals so that the water now empties intothe Mississippi by way of the Illinois River.

(A) Rivers originally flowed into the St. Lawrenceby way of Lake Michigan, but having beenredirected by constructing

(B) Rivers had originally flowed into the St. Lawrenceby way of Lake Michigan, but they have beenredirected by constructing

(C) Rivers, which originally flowed into the St.Lawrence by way of Lake Michigan but have beenredirected by the construction of

(D) Rivers, originally flowing into the St. Lawrenceby way of Lake Michigan, but having been redirected by the construction of

(E) Rivers, originally flowing into the St.Lawrence by way of Lake Michigan, have beenredirected through the construction of

答案选D，为什么这题不能选C呢？不应该有转折关系吗？

蕾咪

我老犯这种低级错误！

oliilo1986

C选项but前面的句子成分不全

DUKB24

C选项木有谓语噢

LZ好好看看

oliilo1986

答案选E才对，so that存在的情况下 用but完全不合理啊