陕西省榆林育才中学高中英语 Unit 4 astronomy Grammar导学案.docVIP

PAGE  陕西省榆林育才中学高中英语 Unit 4astronomy Grammar导学案 学习目标： 了解并掌握主语从句的相关概念； 完成与主语从句相关的练习； 学习重点：it作形式主语的各种句式及虚拟语气的使用。 学习难点：主语从句引导词的正确选择。 预 习 案 课文原句分析(P25-26) 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. The earth became so violent that it was not clear whether the shape would last or not. What is even more important is that as the earth cooled down, water began to appear on its surface. It was not immediately obvious that water was to be fundamental to the development of life. 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. Why they suddenly disappeared still remains a mystery. So whether life will continue on the earth for millions of years to come will depend on whether this problem can be solved. 探 究 案 主语从句：在复合句中充当主语的句子，通常放在主句的谓语动词之前, 或由形式主语it代替，而从句后置放在句子末尾。 句子结构： 引导词 + 句子 + 主句谓语 + 主句其他成分 一、主语从句的引导词 从属连词 that (无意义、无成分、不可省), whether（有意义、无成分、不可省） 连接代词 who(ever), whom(ever), what(ever), which(ever), whose(ver)（有意义、有成分、不可省） 连接副词 when(ever), where(ver), why, how(ever) （有意义、有成分、不可省） That Tom didn’t pass the exam made his mother very worried. Whether we will have a meeting tomorrow hasn’t been decided. What is the most important for us students is studying hard. There are 5 books here. Whichever you will choose is Ok. When and where we will go camping hasn’t been decided. It is not clear why he was absent from school. How we can get enough money is still a problem. 二、如何确定主语从句的引导词 原则：“缺什么补什么” （成分、意义） 1. 如果从句中缺主语、宾语、表语，指人时用who(ever)，whom(ever) 或 which(ever) (有选择范围），指物用what(ever) 或 which(ever) (有范围）； 2. 如果从句中缺状语用when(ever)，where(ver)， why， how(ever)； 3. 如缺定语，用what，which或者whose（修饰名词或代词）； 4. 什么都不缺，用that（无意义）或 whether （有意义“是否”）。 三、形式主语it 有时为了使句子结构平衡, 避免 “头重脚轻”, 常用 it 作形式主语, 把主语从句放在主句的后面。 例如: It is a pity that she has made such a mistake. 这样就构成了下面一些常用句型: 1. It is + n. + 从句 　 It is a pi