Don’t forget the door when you leave.A. closeB. closingC. to closeD. closed

问题补充：

Don’t forget the door when you leave.

A. close

B. closing

C. to close

D. closed

答案：

A. close

B. closing

(答案→)C. to close

D. closed

解析：句意：当你离开的时候，不要忘记关门。固定句型：forget to do sth. 忘记做某事。故选C