Unit 4　Astronomy：the science of the stars

　　重要词汇

重要词汇 相关提示 system n. 系统；体系；制度 牢记该词的基本用法，比如作"系统；体系；制度"讲时是可数名词 theory n. 学说；理论 掌握该词的用法，比如in theory的含义是"理论上" violent adj.猛烈的；激烈的；强暴的 注意该词的基本词义及其副词、名词形式 in time 及时；终于 掌握in time的两个含义以及含time的常用短语 unlike prep.不同；不像 注意unlike的反义词是like harmful adj. 有害的 牢记harm以及harmful的短语 lay eggs下蛋 掌握lay eggs中lay的用法 exist vi. 存在；生存 注意该词的用法及其派生词existence give birth to产生；分娩 牢记该短语的用法以及含birth的相关短语，并注意give birth to 与be born的不同用法 in one's turn轮到某人；接着 注意含名词turn的相关短语 prevent ... from阻止；制止 掌握该短语的用法及其同义词组stop...from和keep...from puzzle n．谜；难题　vi.& vt. (使)迷惑；(使)为难 牢记puzzle作为名词和动词的用法 pull n．& vt. 拉(力)；拖；牵引力 注意pull的用法及其反义词push cheer up 感到高兴；感到振奋 掌握cheer up 既可以作及物动词短语又可以作不及物动词短语的用法 now that 既然 记住now that作连词，其同义词是since，seeing that break out爆发；突发 注意break out不用于被动语态，并记住break的相关短语 watch out密切注视；当心；提防 牢记watch out的用法以及含watch的常用短语 　　重点句型

　　1．What it was to become was uncertain until between 4.5 and 3.8 billion years ago when the dust settled into a solid globe.(what引导主语从句，when引导定语从句)

　　2．The earth became so violent that it was not clear whether the shape would last or not.(so...that...如此......以至于......)

　　3．What many scientists believe is that the continued presence of water allowed the earth to dissolve harmful gases and acids into the oceans and seas.(what引导主语从句，that引导表语从句)

　　4．So whether life will continue on the earth for millions of years to come will depend on whether this problem can be solved.(whether引导主语从句)

　　5．I cheered up immediately and floated weightlessly around in our spaceship cabin watching the earth become smaller and the moon larger.(现在分词短语watching...作伴随状语)

　　重点语法

　　学习主语从句的用法。

写作要求