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Why should I be waiting here without doing anything?我憑什么在這兒白等?。You shouldn’t be thinking about the solution only in one way。如:You should be doing your exercises instead of watching TV。家里這么安靜,我弟弟一定在床上睡覺。他們肯定在離我們不遠的地方尾隨著我們。你一定在想我是從哪兒知道這件事的。4. must后面接進行時表示想必正在做某事。You might be telling me a lie。She might still be crying for being wronged。如:They might be planning to make a loan for their new project。他們可能圣誕節(jié)前回來。她或許明天或者什么時候會動身去紐約。你媽媽可能正等著你回家呢。Can he be still thinking of what I told him?他會不會還在考慮我告訴他的那件事呢?2. may后面接進行時表示可能正在發(fā)生的動作。如:What can she be doing at this moment?這個時候她會在做什么呢?You can’t be telling us the truth。句中有過去時間狀語的,問句部分用過去時,否則,用現(xiàn)在完成時。You might at least have written me a letter。5. could/ might + have done也可用來表示委婉的批評。4. could + have done可用來表示沒做某事的遺憾。如:There is no school today。I should have done my homework last night,but I watched TV instead。如:You should/ ought to have e here earlier。2. should/ ought to + have done在肯定句中表示“該做的事情沒有做”,在否定句中表示“已做了不該做的事”。He can’t/ couldn’t have gone to school。He may/ might not have gone to school。He must have gone to school。如:He could/ may/ might have gone to school。正:We can’t have met before。如:How could he have forgotten such an important thing?(不用may)Might you have met him somewhere?(不用may)(3) must表推測,一般不用于否定句;否定句中應用can或could。I saw her just now。具體使用時請注意以下幾點:(1) can表推測,一般用于疑問句和否定句,極少用于肯定句。這地需要打掃了。注意:need作行為動詞時,還可表示“需要”,后接動名詞的主動形式表示被動含義(詳見“非謂語動詞專題”)。He dared not do it。He didn’t dare(to)do that。I didn’t know whether he dared say that to him。He doesn’t need to do it。如:He needn’t do that。作行為動詞時,有人稱和數(shù)的變化,可用于肯定句、否定句或疑問句中,構(gòu)成否定句或疑問句時要用助動詞do,does,did;作情態(tài)動詞時,沒有人稱和數(shù)的變化(dare可以有過去式dared),直接跟動詞原形,只用于否定句和疑問句中,構(gòu)成否定句和疑問句時不用助動詞?!医裢肀仨毸愠鲞@道題嗎?——不,你不必?;験ou’d better not?!铱梢允褂媚愕能噯幔俊?,不行。7. may作“可以”講時,其否定式常用“mustn’t”表示“禁止”;must作“必須”講時,其否定式是“needn’t”,表示“不必”。如:—How old are you,madam?—If you must know,I’m twice my son’s age。如:Why should you be