②Don't ask me.How should I know?

别问我，我怎么会知道？

5．must的用法

(1)表示"必须"，语气比should，ought to强烈。其否定形式为mustn't (不准；禁止)。

You mustn't do that，because you must keep your word.你不能那么做，因为你得遵守诺言。

考点警示

以must开头的一般疑问句的肯定回答中要用must，否定回答中要用needn't/don't have to。

-Must I finish the paper today?

-Yes，you must./No，you needn't/don't have to.

--今天我必须完成论文吗？

--是的，你必须。/不，你不必。

(2)表示有把握的肯定推测，只能用在肯定句中，意为"一定；准是"；在否定句、疑问句中要用can't代替。

You have worked hard all day.You must be tired.

辛苦工作了一整天，你一定累了。(对现在情况的推测判断)

(3)表示感情色彩，意为"偏偏；偏要"，常指令人不快的事情。

The car must break down just when I was about to start.我正要出发时车偏偏抛锚了。

用适当的情态动词填空

1．In today's information age，the loss of data can cause serious problems for a company.

(2018·北京)

2．Samuel，the tallest boy in our class，can easily reach the books on the top shelf.(2017·北京)

3．You must be careful with the camera.It costs！(2015·四川)

4．You may feel all the training a waste of time，but I'm a hundred percent sure later you'll be grateful you did it.(2015·陕西)

5．It was so noisy that we couldn't hear ourselves speak.(2015·浙江)

6．It was sad to me that they，so poor themselves，should bring me food.(2014·江苏)

7．I still remember my happy childhood when my mother would take me to Disneyland at weekends.(2014·四川)

8．When I was a child，I could watch TV whenever I wanted to.(2013·江西)

Ⅰ.选词填空