职称英语2015年卫生类A级语法辅导：情态动词

　　(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.

　　3.may/might have v-ed

　　may/might have v-ed 表示推测过去某事“也许”发生了。may 比 might 表示的可能性在说话人看来稍大些。例如：

　　I can't find my keys.I may/might have left them at the school yesterday.

　　4.ought to/should have v-ed 和 ought not to/shouldn't have v-ed

　　ought to/should have v-ed 和 ought not to/shouldn't have v-ed 用于对已发生的情况表示“责备”、“不满”，分别表示“本应该…”和“本不应该…”。例如：

　　1)With all the work finished,I should have gone to the party last night.

　　2)You ought not to make fun of him.He is not the one you laugh at but learn from.

　　5.needn't have v-ed

　　needn't have v-ed 表示过去做了某事，但没有做的必要,意为“本没必要…”。例如：

　　You needn't have waken me up; I don't have to go to work today.

　　注：表示推测过去某动作发生的可能性时，就表示的可能性程度而言，must最大，could其次，may更次之，might最小。例如：

　　I wonder how Tom knew about your past.