Unit 2 Discover Useful Structures 课件-2022-2023学年高中英语人教版（2019）选择性必修第三册

Discovering useful structures UNIT 2 HEALTHY LIFESTYLE Contents Lead-in Ⅰ Ⅳ Observe and Discover Ⅱ Ⅲ Practice and Apply Homework Ⅰ Lead-in 3 Lead-in Analyze what does the underlined part serve as in each sentence and translate them into Chinese. To prevent harmful habits like these from dominating a teenager’s life is essential. (para 1) To change bad habit is never easy,even with many attempts. (para 2) 改变不良习惯从来都不是一件容易的事情，即使你三番五次地尝试。 防止此类有害习惯主宰青少年的生活是至关重要的。 系动词 表语 主语 主语 系动词 表语 to do 不定式放在句首作主语 Lead-in It took the surgeon three hours to finish my mother’s lung surgery. To join the People’s Liberation Army, it is required for men to shave off their beards. It was not polite to disturb your neighbours with loud music last night. Read the following sentences and analyze what does the underlined part serve as in each sentence. (activity 1) 形式主语 真正主语 形式主语 真正主语 形式主语 真正主语 用 it 作形式主语，放在句首，把真正的主语 — 动词不定式置于句后。 How to use the computer is a question. Lead-in When to go there has not been decided yet. Try to find the subject of each sentence, and translate them into Chinese. 主语 主语 如何使用电脑是一个问题。 还没决定什么时候去那里。 疑问词+不定式作主语 动词不定式作主语有三种形式： 直接放在________作主语； 为了保持句子平衡，用________作形式主语，放在句首，把真正的主语 — 动词不定式置于句后； 和_________构成短语作主语。 句首 it 疑问词 Summary Lead-in II Observe and Discover 8 Observe and Discover 1. To see is to believe. 2. To do this is to cut the foot to fit the shoe. 3. To say is one thing and to do is another. 4. To make a detailed plan is a good idea to make it successful. 从位置上看，动词不定式作主语，通常放在句首。当句子主语和表语都是非谓语时，通常要_________，例如： To see is to believe. = Seeing is believing. 保持一致 Observation 1 Observe and Discover For him to admit his mistakes is not easy. For us to finish the composition in a quarter of an hour is really difficult. 动词不定式作主语可以带上自己的____________，一般用for / of 短语来表示。但此时多使用形式主语 it 来引起，使得句子保持平衡。例如，第2句可以改为：It is really difficult for us to finish the composition in a quarter of an hour. 逻辑主语 Observation 2 Observe and Discover Observation 3 1. To be working all day long is a