The scientists were waiting to see the problem . A. settleB. to settle C. settledD. settl

问题补充：

The scientists were waiting to see the problem .

A. settle

B. to settle

C. settled

D. settling

答案：

A. settle

B. to settle

C. settled

D. settling

解析：在感官动词see后面用过去分词作宾补，表示“看到……被……”。