小伙伴们，公共英语考试大家复习的怎么样了呢？下面是帮考网分享的一些公共英语考试二级部分的语法资料，一起来看看吧！

二级pets2语法总结(6)

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

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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