Don’t forget the door when you leave.A. closeB. closedC. to closeD. closing

问题补充：

Don’t forget the door when you leave.

A. close

B. closed

C. to close

D. closing

答案：

A. close

B. closed

(答案→)C. to close

D. closing

解析：根据语境可知此句的含义是离开的时候不要忘记关门，考查的固定句型结构forget to do sth表示忘记做某事。由选择项的提示可知选择C。