单选题
17. By the time he arrives in Beijing,we ______ here for two days.
A) will have stayed C) have been staying
B) shall stay D) have stayed
【正确答案】
A
【答案解析】词组by the time意为“在…之前”，它引导的句子用现在时表示将来时间，故主句需用将来时。再由stay这个动作一直持续着，故用完成时。结合以上两点，故选A。句意：在他到达北京之前，我们将在这儿住了两天。