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1) since+过去一个时间点(如具体的年、月、日期、钟点、 1980, last month, half past six)。
例如: I have been here since 1989. 1989起,我一直在这儿。
2) since+一段时间+ ago。
例如: I have been here since five months ago. 我在这儿,已经有五个月了。
3) since+从句。
例如: Great changes have taken place since you left. 你走后,变化可大了。
4) It is+一段时间+ since从句。
例如: It is two years since I became a postgraduate student. 我考上研究生有两年了。
【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。
例如:
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……"。
例如: 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
- - - 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。