11.14 延续动词与瞬间动词
 
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。