The program was so exciting that the children kept their eyes on the screen.A. to fixB. t

问题补充：

The program was so exciting that the children kept their eyes on the screen.

A. to fix

B. to be fixed

C. fixed

D. fixing

答案：

A. to fix

B. to be fixed

(答案→)C. fixed

D. fixing

解析：由固定结构fix one’s eyes on/upon...可知此处应用过去分词。