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1、be supposed to do的用法be supposed to do在本单元中是“应该;被期望;理应”之意。用来表示根据规定,人们不得不做的事,或期待发生的事。时态、人称和句式的变化在be动词上体现,to为不定式符号,后接动词原形。其用法如下:1.be supposed to do的肯定句式be supposed to do的肯定句式,be动词随主语的变化而变化,to后接动词原形。例句:Youre supposed to start work at 8:30 every morning. 你应该每天早晨8:30开始工作。The train was supposed to arrive h
2、alf an hour ago. 火车本应该在半小时之前到达。2.be supposed to do的否定句式be supposed to do的否定句式即在be动词后加否定词not,此时相当于be not allowed to do, 意为“不被许可;不应当”。例句:We are not supposed to play football in the street. 我们不应该在大街上踢足球。It is a secret still. I am not supposed to say it out. 这还是个秘密,我不能说出来。3.be supposed to do的疑问句式be supp
3、osed to do的疑问句式需将be的相应形式提到主语前。例句:Is he supposed to get there at five? 他应该在五点钟到那儿吗?Was Lucy supposed to speak Chinese like that? 露西应该像那样说汉语吗?(1)当be supposed to的主语是“人”时,意为“应该;被期望”,此时可以用来表示劝告、建议、义务、责任等,相当于情态动词should。例句:Youre supposed to tell him if you want to leave. 如果你要离开,应该先告诉他。(2)当be supposed to的主语是“物”时,意为“本应;本该”,用于表示某事本应该发生而没发生。例句:The meeting is supposed to take place on Tuesday, but we have to put it off. 这次会议本应在星期二举行,但我们不得不把它推迟。