1) 用于完成时的区别 延续动词表示经验、经历； 瞬间动词表示行为的结 果，不能与表示段的时间状语连用。 He has completed the work. 他已完成了那项工作。 (表结果) I ve known him since then. 我从那时起就认识他了。(表经历)
2) 用于till / until从句的差异 延续动词用于肯定句，表示"做……直到……" 瞬间动词用于否定句，表示"到……，才……" He didn t come back until ten o clock. 他到10 点才回来。 He slept until ten o clock. 他一直睡到10点。
典型例题 1. You don t need to describe her. I ___ her several times. A. had met B. have met C. met D. meet 答案B. 首先本题后句强调对现在的影响，我知道她的模样，你不用描述。再次，several times告知为反复发生的动作，因此用现在完成时。
2.---I m sorry to keep you waiting. ---Oh, not at all. I ___ here only a few minutes. A. have been B. had been C. was D. will be 答案A. 等待的动作由过去开始，持续到现在，应用现在完成时。