【题目】They have been waiting for hours to see the singer，but the airplane must have been ________.
A. behind the times B. behind schedule
C. ahead of time D. in no time
在线课程【答案】B
【解析】考查介词词组。behind schedule“晚点”；behind the times“过时，跟不上时代”；ahead of time“提前”；in no time“立即，马上”。根据句意可知选B。