The people there did not allow them to set up a factory pollute the water in the river.A.

问题补充：

The people there did not allow them to set up a factory pollute the water in the river.

A. not so as to

B. so as not to

C. in order to

D. so that

答案：

A. not so as to

(答案→)B. so as not to

C. in order to

D. so that

解析：

句意是;为了不污染水，那里的人不允许他们建工厂，so as not to do “为了不…”。选B。