2018年12月英语六级语法常考知识点讲解汇总
　　英语六级语法常考知识点讲解：动词时态
　　1)现在完成进行时态 (have/has been -ing 分词构成): 动作或状态从过去某时开始,继续到现在,可能继续下去,也可能刚刚结束.
　　I’ve been writing letters for an hour.
　　I’ve been sitting in the garden.
　　2)过去完成进行时(由had been ing分词构成): 过去某个时刻以前一直在进行的动作
　　I’d been working for some time when he called.
　　We had been waiting for her for two hours by the time she came.
　　3)将来完成进行时: 将来某个时刻以前一直在进行的动作.
　　By next summer, he will have been working here for twenty years.
　　In another month’s time she’ll have been studying here for three years.
　　4)将来完成时(由shall/will have 过去分词构成): 将来某时会业已发生的事.
　　I shall have finished this one before lunch.
　　They’ll have hit the year’s target by the end of October.