求助885 sec_1_18

18.   School integration plans that involve busing between suburban and central-city areas have contributed, according to a recent study, to significant increases in housing integration, which, in turn, reduces any future need for busing.

(A) significant increases in housing integration, which, in turn, reduces

(B) significant integration increases in housing, which, in turn, reduces

(C) increase housing integration significantly, which, in turn, reduces

(D) increase housing integration significantly, in turn reducing（A）

(E) significantly increase housing integration, which, in turn, reduce

    这道题不明白为什么选A ，请哪位大虾指点一下。

我选择D。

判断：1) increase用动词形式

2) significantly表示明显的

3) which指代？

可标准答案给的为什么是A呢?