英语六级语法知识：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。

英语六级语法知识：since的四种用法

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)。

I have been here since 1989.

2) since +一段时间+ ago

I have been here since five months ago.

3) since +从句

Great changes have taken place since you left.

Considerable time has elapsed since we have been here.

4) It is +一段时间+ since从句

It is two years since I became a postgraduate student.

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