1. The man we followed suddenly stopped and looked as if ______ whether he was going in the right direction.

A. seeing                  B. to see             C. having seen                  D. to have seen

2. A new law has been passed in response ______ the rare animals.

A. to kill                 B. of killing             C. to killing             D. for killing

3. ________waste water was put into the rivers and lakes, which were badly polluted.

A. At one time     B. At a time          C. One time        D. A time