1、Book 3 Unit 4 重点短语讲解1. They were in time to produce carbon, nitrogen, water vapour and other gases, which were to make the earths atmosphere. (P25)【归纳】 in time (1) 及时。如：I was just in time for the flight.(2) 总有一天，迟早。相当于sooner or later; eventually。如：Dont give up and you will succeed in time.【延伸】 all t
2、he time一直，始终，老是；at a time一次；at one time曾经，一度；at times经常；by the time到的时候为止；for the time being暂时；take ones time不着急，慢慢来；of the time当代的，当时的。【易错点】 及时做某事：in time for sth / to do sth。如：Will I be in time for the train / to catch the train?2. They are putting too much carbon dioxide into the atmosphere, whic
3、h prevents heat from escaping from the earth into space. (P26)【归纳】 prevent sb / sth (from) doing sth阻止某人或者某事做某事【延伸】 与这种结构相似的有stop sb / sth (from) doing sth （from可以省略）和keep sb / sth from doing sth （from不可以省略）。【易错点】 prevent sb / sth(from) doing sth 在主动语态中from可以省略，但是在被动语态中from不可以省略。3. So whether life w
4、ill continue on the earth for millions of years to come will depend on whether this problem can be solved. (P26)【归纳】 depend on / upon意为“依靠，依赖”，常用结构是 depend on sb / sth，depend on sb to do sth。【延伸】 depend on it常用于句首或句末，意为“请放心，没问题”；It alldepends和That depends意为“看情况而定”，二者都用于口语中。如：Depend on it, hell turn
5、up.It depends on how you deal with the problem. 【易错点】 depend on 后接表示“是否”的从句时，只用whether, 不用if。如：It depends on whether you want to do it or not.4. We watched, amazed as fire broke out on the outside of the space-ship as the earths gravity increased. (P31)【归纳】 break out 可指大火、战争等突然爆发。如：It was almost mid
6、night that a fire broke out in the neighborhood.【延伸】 break down毁掉，倒塌，分解；break in破门而入，打断，插嘴；break into强行闯进；break off中断，中止；break up打碎, 终止，结束。【易错点】 break out是不及物动词，后面不能跟宾语，没有被动语态。如：World War broke out in 1939.5. I cheered up immediately and floated weightlessly around in our spaceship cabin watching th
7、e earth become smaller and the moon larger. (P31)【归纳】 (1) cheer up是常用来鼓励别人的话，作为及物动词短语，意为“使高兴，使情绪好转”。如：Lets cheer him up. He looks blue. (2) cheer up作不及物动词短语，意为“高兴起来，振作起来”。如： Cheer up! Things are not so bad as they seem. 【延伸】 Cheers! 干杯；cheer on鼓劲，加油；cheering squad啦啦队；cheerleader啦啦队队长。【易错点】 cheer up作及物动词短语时，如果宾语是人称代词，要放在cheer up的中间；如果是名词，既可以放在cheer up的中间，也可以放在cheer up的后面。如：He made faces to cheer up his sister.She told a joke, trying to cheer me up.
