When the summer comes，the day is getting longer and longer，and the night(is getting) shorter and shorter.夏天来的时候，白天越来越长，而夜晚越来越短。

　　3．主从复合句中的省略：

　　(1)主句中有些成分可以省略，特别是句首。

　　Pity you couldn't come to see their wonderful performance.(＝It was a pity that you couldn't come to see their wonderful performance.)很遗憾你没有来看他们精彩的表演。

　　(2)省略从句中与主句相同的部分。

　　I have a good opinion of soldiers，but I don't know why (I have a good opinion of soldiers)．

　　我对士兵有好感，但不知道为什么。

　　(3)省略一个从句或从句的一部分，用so或not(但不可用it或that)代替。

　　-Will he be able to pass the College Entrance Examination next year?

　　--他能通过明年的入学考试吗？

　　-I believe so.(＝I believe that he will be able to pass...)

　　--我相信会的。

　　-Do you think I will achieve success?

　　--你认为我能成功吗？

　　-I'm afraid not.

　　--恐怕不行。

　　(4)主句和从句中各有些成分被省略。

　　The sooner，the better.(＝The sooner you do it，the better it will be.)越早越好。

　　4．其他省略：

　　(1)连词that的省略：

　　宾语从句中常可省略连词that，但多个that引导的宾语从句并列时只可以省略第一个that。由it作形式宾语时，引导宾语从句的that也不能省略。

　　He said (that) he would come and that he would stay here for only an hour.他说他能来，但只能待一个小时。

　　I think it necessary that you should read English every day.

　　我认为你每天读英语是很有必要的。

　　关系代词在定语从句中作宾语、表语或在定语从句中用于there be句型时，that也可以省略。

　　This is the happiest day (that) I have ever spent in all my life.这是我一生中度过的最快乐的一天。

　　China is not the country (that) she used to be.

　　中国不再是以前那样。

　　This is the fastest train (that) there is to Shanghai.

　　这是去上海的最快列车。

　　(2)不定式符号to的省略：

　　①并列的不定式，前面的不定式带to，后面的to可省去，但如果两个不定式之间有对比关系时，则不可以省去to。

　　I told him to sit down and wait for a moment.

　　我告诉他坐下来等一会儿。

To go home or to stay at school during the vacation is not decided yet.假期期间回家或待在学校还没有决定。