看看这个句子：

It's been six years since we last saw each other. 我们6年没见面了。

意为“自从…至今已经多久了”。 (从句中的动作是短暂性的)

意为“自从不…至今已经多久了”。 (从句中的动作是延续性的)

此句式中，确定since从句中的动词是短暂性动词还是延续性动词是能否正确理解句意的关键所在。

It's ten years since he came to Shanghai. = He has lived in Shanghai for ten years.

他来上海已经十年了。

It's ten years since he left Shanghai. =He has lived outside Shanghai for ten years.

他离开上海已经十年了。

It is two years since my elder brother joined the army. 我哥哥参军已两年了。

It is two years since my father smoked. 我爸爸已戒烟（不抽烟）两年了。

注意：since从句通常用一般过去时，其谓语动词的延续与否决定了句子含义的不同。另外，这种结构中，since后面不能用否定式。

典型错误：It's a long time since you didn't come to see me.

It will be two weeks before he recovers. 他需要两周的时间才能恢复。

It was six o'clock when we got home last night. 昨天晚上我们到家时已经6点了。

It was at six o'clock that we got home last night. 昨天晚上我们是在6点钟到家的。

This is the first time I have visited your hometown. 这是我第一次来到你的家乡。

This is the third time this week that he has been late for work. 这已是他本周第三次上班迟到了。

That was the last time that he had seen her. 那是他最后一次看见她。

This is the first time that I have drunk so nice beer. 这是我第一次喝如此好喝的啤酒。

注意：此句型中，1：如果主句用is，则 that从句中用现在完成时；如果主句用 was，则that从句中用过去完成时；2：主句不用完成时态。本句型时态的考查是重点，记住！！！

典例 1

That was really a splendid evening. It's years （ ）I enjoyed myself so much.

A. when B. that C. before D. since

典例 2

It was some time （ ） we realized the truth.

A. when B. until C. since D. before

典例 3

This is the first time we （ ） a film in the cinema together as a family.

A. see B. had seen C. saw D. have seen

解析1：后句句意：多年没有玩得这么快活了。since从句后跟延续性动词，表示该动作的结束。又如：It's three years since I smoked. (自从）我戒烟已经三年了。 答案：D

解析2：it is/was/will be + 一段时间 + before…，“过一段时间，才…”，表示某一动作从现在起到将来某时刻之前发生的这一段时间的总和，也可指某一动作从过去某时刻起直到另一过去时刻发生之前的若干时间。 答案：D

解析3：句意：这是第一次我们全家人一起到电影院看电影。This/It is the first/second time that… 句型中，从句的谓语动词用现在完成式。 答案：D

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