构成:have been doing sth. 用法:表示从过去某一时间开始一直延续到现在的动作。这个动作可能刚刚结束,也可能仍在继续,并可能延续到将来。(表示到现在为止一直在发生或反复进行的动作) ––– How long have you been waiting here? ––– I have been waiting here ...
We are going to have a meeting today. 3) be to + 动词原形 表示按计划或安排即将要发生的动作: He is to visit Japan next year. We are to discuss the report on Monday. 4) be ab...
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