2015年职称英语考试卫生类语法:情态动词(1)
2014-05-20 14:08 来源:医学教育网
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情态动词(Model Verbs) 又称为情态助动词(Model Auxil-iaries)。英语中助动词主要有两类:一是基本助动词,如have,do,be;二是情态助动词,如may,must,need等。情态动词与其他动词连用表示说话人的语气。情态动词可表达建议、要求、可能和意愿等。情态动词没有人称和数的变化。在大学英语四、六级考试中,情态动词部分重点测试以下内容:
(1)情态动词+行为动词完成式
(2)情态动词+行为动词进行式
(3)情态动词+行为动词完成进行式
(4)某些情态动词的特殊用法
一、情态动词+行为动词完成式
情态动词+行为动词完成式即“情态动词+ have + v-ed分词”,表示对过去行为或动作进行推测、评论或判断。
1. must have v-ed
must have v-ed 表示推测过去某事“一定”发生了。其否定形式为:can't/couldn't have v-ed,表示过去不可能发生某事。例如:
1)Since the ditch is full of water,it must have rained last night.
2)You couldn't have met my grandmother. She died before you were born.
2. could have v-ed
could have v-ed 表示推测过去某动作“很可能”发生了。例如:
1)The dictionary has disappeared. Who could have taken it?
2)Tom could have taken it. He was alone yesterday.
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