问题补充：
Mr. Black Shanghai in a few days. Do you know when the earliest plane on Sunday.
A. leaves; takes off
B. is leaving; takes off
C. is leaving; is taking off
D. leaves; is taking off
答案：
A. leaves; takes off
(答案→)B. is leaving; takes off
C. is leaving; is taking off
D. leaves; is taking off
解析：句意：Mr Black几天后将离开上海。您知道周日最早的航班是什么时间吗？用现在进行时表将来通常含有“意图”“安排”“打算”等义。这种现在进行时比较生动，给人一种期待感，通常用于表最近或较近的将来，偶尔也可表示较远的将来，所用动词通常表示位置移动的动词。如：come，go，move，arrive，leave等。Annie is coming to supper this evening. 安妮今晚要来吃饭。When I grow up, I’m joining the army. 我长大了要参军。come, go, arrive, leave, start, begin, return的一般现在时表将来，这主要用来表示在时间上已确定或安排好的事情，如飞机起飞等。The train leaves at six tomorrow morning.火车明天早晨6点发车。故选B。
