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Maybe C. May I swim here? I’m sorry. Children ____swim alone here Must。 can’t B. May。 must Can。 mustn’t D. Can’t。 can 4. Must 的用法 ⑴ must表示“一定要,必須”。否定形式是 mustn’ t,表示 “禁止,不許可”。 eg: You must stay here until I came back. You mustn’ t park your car in front of the entrance. ⑵ 對(duì) must引導(dǎo)的疑問(wèn)句,肯定回答為 must,否定回答為 needn’ t或者 don’ t have to。 eg: Must I finish my homework now? No, you needn’ t. ⑶ must 常常指有根據(jù)的,比較有把握的推測(cè),意為 “一定是,準(zhǔn)是”,這種用法只能用于肯定句當(dāng)中。 eg: The light is on. He must be at home now. 當(dāng) must表示肯定判斷、推測(cè)的時(shí)候,其反意疑問(wèn)句要用實(shí)際問(wèn)句的助動(dòng)詞來(lái)構(gòu)成。 eg: She must have finish writing, hasn’t she? ⑷ must 和 have to ① must側(cè)重于個(gè)人意志和主觀(guān)上的必要,意為“必須,應(yīng) 該”。 eg: I know I must study hard. ② have to 側(cè)重于客觀(guān)上的必要,意為“不得不”。它有一 般現(xiàn)在時(shí)第三人稱(chēng)單數(shù)形式 has to 和過(guò)去形式 had to。 eg: My brother was very ill, so I had to call the doctor at midnight. ③ have to的否定形式是 don’ t have to, 相當(dāng)于 needn’ t, 意為“不必”; mustn’ t 表示“禁止,不允許” . (5) can’t 和 mustn’t 表否定推測(cè)時(shí)應(yīng)用 can’t, mustn’t 意為“禁止,不允許”,不用來(lái)表推測(cè),在肯定句中用 must表推測(cè),意為“一定” Mom, must I clean my room now? No, you can do it tomorrow. A. can’t B. needn’t C. mustn’t D. shouldn’t 的用法 ⑴ need表示“需要 , 必須”,主要用于否定句和疑問(wèn)句當(dāng)中,否定形式為 needn’ t,意為“沒(méi)有必要,不必”。用 need提問(wèn)時(shí),肯定回答是 must,否定回答為 needn’ t. eg: Need I stay here any longer? ⑵ need可作實(shí)義動(dòng)詞,此時(shí)還有人稱(chēng),數(shù)和時(shí)態(tài)的變化,后面多接動(dòng)詞不定時(shí)。 eg: I need to do it right now. He needs to learn more about the girl. 注意 : 對(duì) need 的詞性判斷常為難點(diǎn), need后加 to do說(shuō)明need為實(shí)義動(dòng)詞,用助動(dòng)詞提問(wèn)或否定; need后加 doing表示被動(dòng)意義;若 need 后加 do的動(dòng)詞原形,則 need為情態(tài)動(dòng)詞 You needn’t see him, but I must. You don’t need to e if you feel sick. (6). dare 表示 “敢于 ”, 用作情態(tài)動(dòng)詞時(shí),無(wú)人稱(chēng)變化,只用于否定句、疑問(wèn)句和條件句 Mary dare not touch the snake. 用于實(shí)義動(dòng)詞時(shí),要注意人稱(chēng)和時(shí)