二零二三年 优质公开课Unit8Lesson22FamousDiscoveries教学.ppt

Unit 8 Lesson 22 Famous Discoveries Think about it If we learn more about DNA, we will be able to treat more diseases. Is this a real situation? Can we learn more about DNA? Read the passage and underline the sentences like this. If we learn more about DNA, we will be able to treat more diseases. If we do not use them correctly, they can cause serious health problems. If we discover more about the human body, we can help people live longer and better lives. Which expresses the result if the condition happens? Which part of the sentence, which clause, expresses the condition? If we discover more about the human body, we can help people live longer and better lives. 从句 主句 If I ______ (have) time, I __________ (visit) my grandparents. If you _____ (have) any questions, you __________ (ask) Kim for help. have will visit have can ask 条件状语从句主要由if或unless引导。 if是连词，意为“如果；假如”。 unless，意为“除非；如果不”，通常可以和if ... not互换使用。 条件状语从句 e.g. If it rains tomorrow, they won’t go out. I won’t write unless he writes first. = I won’t write if he doesn’t write first. if引导的条件状语从句通常表示一种假设的条件，即如果从句的动作发生，则主句的动作有可能会发生。 通常情况下，如果主句用一般将来时，if 引导的条件状语从句用一般现在时。 e.g. If it rains, I’ll stay at home. 如果主句是祈使句或者主句的谓语部分 含有情态动词，if引导的条件状语从句也 常用一般现在时。 e.g. Please tell Tom about it if he comes back. You must study hard if you want to get good grades. 主句没有用一般将来时，而是用了一般 现在时。这是条件状语从句运用时的一 个特殊情况：如果句子表示“客观事 实”，主句和从句通常都用一般现在时。 e.g. If baby dogs are in danger, their mother attacks people. 条件状语从句 结构 时态 主句 + 引导词 + 从句 引导词 + 从句， 主句 主句将来时，从句现在时 主句过去时，从句过去时 主句祈使句，从句现在时 主句情态动词，从句现在时 What can/will you do if .... · there is a fire? · there is an earthquake? · your bike is broken on your way to school? · you get lost? Talk about the discoveries in Exercise 2. Which do you think is the most important? Example A: I think X-rays are the most important discovery. B: Because with X-rays, doctors can help fix broken bones more easily. C: … People now live lon