Hearing the news we did nothing but silently.A. to sitB. satC. to be sittingD. sit

问题补充：

Hearing the news, we did nothing but silently.

A. to sit

B. sat

C. to be sitting

D. sit

答案：

A. to sit

B. sat

C. to be sitting

(答案→)D. sit

解析：考察固定用法。Do nothing but do sth除了做…之外无事可做；因为but前面有动词do的某种形式，使用省略不定式符号to.故A正确。