【正文】 to e tomorrow. 在回答 must的疑問句時(shí)，否定回答常用 needn’t 或 don’t have to表示不必，而不用 mustn’t 。 1. 表示能夠或不能做某事用 can 或 can’t A bird can fly . Fish can’t live without water. 2. 告訴人們必須或禁止做某事用 must或 mustn’t You must hand in your homework at once. You mustn’t talk loudly in public. 3. 表示請求或允許做某事 may 或 can May I e in ? Can I open the door ? 4 .談?wù)撛撟龌虿辉撟瞿呈掠?should , ought to 或 shouldn’t , ought not to She should do her homework first . They ought to finish the work on time . they ought not to be late for school . ★★★ Notes : can 和 be able to的區(qū)別 : be able to 有 人稱數(shù)和時(shí)態(tài)的變化。Unit 4 Electricity electricity n. 電 electrician n. 電工 There is a problem with the electricity in Tom’s flat . An electrician has e to deal with it . electric a. 電的 electric storm electric shock electrical a. 電氣科學(xué)的 electrical apparatus 電器 electrical engineer Words and expressions in Reading A What do you know about: change v/n. 變化 We can’t see electricity , but we can change it into energy . Great changes have taken place in Shenzhen since 1980. changeable a. The weather is changeable on top of the mountain . n. 找頭；（找回的）零錢 Here is your change. energy n. Young people usually have more energy than the old. 年輕人通常比老年人有活力。 The envelop contains some photos of her family. Phrases : 1. 轉(zhuǎn)化 ,變成 2. 戲弄某人 3. 最后 4. 看上去很傻 5. 流經(jīng) 6. 某種意義上 7. 看電纜聯(lián)結(jié)在一起 8. 電燈泡 9. 撓頭 10. 不同形式的能量 11. 發(fā)電站 change into trick sb at last look foolish flow through in a way be connected to cables a light bulb