This means going back to the place where we left the family in a tree the night before.A.

问题补充：

This means going back to the place where we left the family in a tree the night before.

A. to sleep

B. to be sleeping

C. slept

D. sleeping

答案：

A. to sleep

B. to be sleeping

C. slept

(答案→)D. sleeping

解析： 考查非谓语。the family与sleep为主谓关系所以用现在分词作补语。句意：这意味着我们要返回前天晚上这一家睡觉的地方。