It is句型

Since用法小结
a) Since后面的动词不同，动作的起算时间不同： since+终止性动词的过去式，从该动作发生时算起；since+ 延续性动词的过去式，从该动作结束时算起。 It’s three years since he joined the League. 他入团三年了。 It is three years since he smoked.他戒烟三年了。 区别：他吸烟已经三年了。He has smoked for three years. b)“ It is/was + 一段时间+ since – clause” 句型的时态。 It’s two years since we arrived here. 我们到这儿两年了。 It was years since I had seen her. 我认识她好几年了。


③How long do you think it will be ______ the computer company puts forward a new product? A. before B. since C. until D. that [解析]A。How long属于时间段，故选A。




④It is +时间状语 +that…属于强调句。 It was at eight o’clock that he came back home. 他是在八点钟回家的。 【典型例题】 ①—Did Jaxk come back early last night? —Yes. It was not eight o’clock ______ he arrived home. A. before B. that C. when D. until [解析]C。此处eight o’clock前没有介词，不是强调句， 可排除B；eight o’clock为时间点，而before前面的主 句应用时间段，可排除A；until主句的谓语动词应是 非延续性，而此处为延续的was，可排除D；故C为本 题的答案。句意：“杰克昨晚回家早吗？”“是的， 当他回家时还不到八点。”



③It is +时间段 +since…“自从……以来已经多 久了”； It is two years since he joined the army. 他参军已经两年了。(从句谓语动词为非延续 动词) It is three years since I smoked a cigar. 我不吸烟已有三年了。(从句谓语动词为延续 动词)



④How long do you suppose it is ______ he arrived there? A. when B. before C, after D. since [解析]D。How long属于时间段，可排除A，因 为when前面的主句一般为时间点；此处也不 能用before和after，因为时态有误；故D为最 佳答案。
Biblioteka Baidu

②How long do you think ______ the computer company launches a new model? A. it will be before B. will it be until C. will it be when D. it will be that [解析]A。do you think为插入语，可知此处应 用陈述语气，排除B、C两项；此处不是强调 句，可排除D；How long属于时间段，故选A。
“It is +时间+连词……” 句式讲解





①It is + 时间段 +before…“过了多久之后才 ……”； He became an actor at a very young age, but it was 20 years before he became famous. 他很年轻就当了演员，但过了二十年后才 出名。 ②It is + 时间点 +when…“当……时是几点 钟”； It was eleven o’clock when he came back home. 当他回家时已经十一点了。