每课一句：新概念英语第1册第129课
【往期回顾】
接下来，我们就来看看第129课的“每课一句”。
一、课文原文
Lesson 129 Seventy miles an hour
Look, Gary! That policeman’s waving to you. He wants you to stop.
Where do you think you are? On a race track? You must have been driving at seventy miles an hour.
I can’t have been.
I was doing eighty when I overtook you.
Didn’t you see the speed limit?
I’m afraid I didn’t, officer. I must have been dreaming.
He wasn’t dreaming, officer. I was telling him to drive slowly.
That’s why I didn’t see the sign.
Let me see your driving licence.
I won’t charge you this time. But you’d better not do it again!
Thank you. I’ll certainly be more careful.
I told you to drive slowly, Gary.
You always tell me to drive slowly, darling.
Well, next time you’d better take my advice!
——选自《新概念英语》第一册，外语教学与研究出版社，1997年10月第1版
二、每课一句
You must have been driving at seventy miles an hour.
本课开始学习情态动词must与can't表猜测的用法，在第127课里学习的是针对现在的状态和动作的猜测，请参看下面的文章：
每课一句：新概念英语第1册第127课
本课侧重的是must与can't表对过去的状态和动作的猜测。
一、must
must表肯定猜测，意思是“一定；肯定”，其基本用法为：
状态：主语+must+have been+形容词/名词/短语
动作：主语+must+have been doing
如：
He must have been tired.
He must have been a teacher.
He must have been at home just now.
He must have been sleeping at home yesterday afternoon.
二、can't
can't表否定猜测，意思是“一定不；肯定不”，其基本用法为：
状态：主语+can't+have been+形容词/名词/短语
动作：主语+can't+have been doing
如：
He can't have been tired.
He can't have been a teacher.
He can't have been at home just now.
He can't have been sleeping at home yesterday afternoon.
【注意】
当表对过去的动作的猜测的时候，如果不强调该动作的持续进行，而是强调过去做过某事的话，其用法为：
sb. must/can't have done
如：
She must have finished her work, otherwise she can't be playing with her friends.
她肯定已经完成了作业，否则的话她现在不可能和她的朋友一起在玩。
He can't have done that, for he is not that kind of man.
他不可能这么做的，因为他不是那种人。
三、更多拓展
That's why I didn't see the sign.
注意本句话中的谓语动词采用了一般过去时didn't see，这是因为说话者Gary是对Ann上面提到的过去发生的事情的回应。
此外，这句话也有一定的诙谐效果，因为Gary想表达的是：
正是因为Ann当时一直不停地提醒他要开慢点，反倒影响了他注意观察路牌了。
