I clean the blackboard every day. Ill clean the blackboard in several minutes. Im now cleaning the blackboard. I cleaned the blackboard several minutes ago. I have cleaned the blackboard for several minutes. I have been cleaning the blackboard for several minutes / since several minutes ago.现在完成时和现在完成进行时的区别 I (1)表示从过去某一时间开始一直在 进行的动作, 并有可能持续下去, 强调动作的全过程； 表示从过去到现在的重复性动作 。 (2)注意:多用于延续性动词，如 work, live, study, skate, collect 表示在某一特定时间之前曾经发生过的动作 ,或者到这一时间为止已经完成的动作. 1.现在完成时: have + 过去分词 2.现在完成进行时:have
