up late at night is bad for your health.A. StayB. StayingC. staysD. Stayed

问题补充：

up late at night is bad for your health.

A. Stay

B. Staying

C. stays

D. Stayed

答案：

A. Stay

(答案→)B. Staying

C. stays

D. Stayed

解析：

试题分析:此句的含义表示晚上熬夜对身体有害。根据语境可知作主语要用动词的非谓语形式，由四个选择项提示可知只能选择动名词短语，故选B。