Unit 4 Breaking boundaries Using language课件 -2022-2023学年高中英语外研版选择性必修第二册

　UNIT 4　 Breaking boundaries --- Using language 1. Students could learn some words and phrases. 2. Students could undestand the main usage of this grammar. 3. Students could write some a passage by using this grammar. Learning Aims: What is your understanding of this grammar？ Share you ideas with others it 做形式主语 It as an empty subject Before learning, please try to write some sentences by using this grammar---“It as an empty subject”. Brainstorming:Before learning this grammar, what grammars come to your mind? 1. subject 2.the usage of it 3... Try to write your opinions in your notebook! It as an empty subject Answer the questions. a　But it is vital not to take any chances. b　But not to take any chances is vital. c　It is important to remember that Ebola doesn’t respect national boundaries. d　To remember that Ebola doesn’t respect national boundaries is important. 1　What does “it” refer to in sentences (a) and (c)? “not to take any chances” “to remember that ...boundaries” 7 Answer the questions. a　But it is vital not to take any chances. b　But not to take any chances is vital. c　It is important to remember that Ebola doesn’t respect national boundaries. d　To remember that Ebola doesn’t respect national boundaries is important. What is the difference between the two groups? The first sentences in each group use “it” as an empty subject and the other sentence are not 8 Answer the questions. a　But it is vital not to take any chances. b　But not to take any chances is vital. c　It is important to remember that Ebola doesn’t respect national boundaries. d　To remember that Ebola doesn’t respect national boundaries is important. Why does the author choose to use sentences (a) and (c)? These sentences are balanced and the information is clear. 9 当不定式（短语）、动名词（短语）或从句在某个句子中作主语时，为保持句子结构前后平衡，避免头重脚轻，因此常用it作形式主语置于句首，而将真正的主语放在句尾。此时it只起先行引导作用，本身无词义。 e.g. It is wrong to tell a lie. (说谎是错误的。) 〔It为to tell a lie的形式主语〕 It is no use arguing about it. (争吵是没用的。) 〔It为arguing abo