问题补充：
Whoever leaves the room last must that all the lights are turned off.
A. is sure
B. make sure
C. find out
D. look out
答案：
A. is sure
(答案→)B. make sure
C. find out
D. look out
解析：短语必须。B确定；C发现，查明；D当心；A项不能放在must的后面。句意：任何一个最后离开房间的人必须确定所有的灯都被关闭了。根据句意说明B正确。
