马 英语单选作文是硬伤

只是想和大家分享一下，大家没事的时候就可以看一下。

不要沉。。

3.must的基本用法
(1)must表示“必须”“应该”之意，其否定式为must not,缩写形式为mustn't,表示“不应该”“不准”“不许可”或“禁止”之意，如:We must study hard and progress every day.
You mustn't touch the fire.(2)对以must提出的疑问句，如作否定回答，要用needn't或don't/doesn't have to(不必)来回答，而不用mustn't,因为mustn't表示的是“禁止”或“不许可”之意，如:--Must we finish the work tomorrow?--No,you needn't/don't have to,but you must finish it in three days.

(3)在肯定句中must可以表示推测，表示“一定”或“必定”之意，如:--Whose new bike can it be?--It must be Liu Dong`s.I know his father has just bought him a new one.

4.can could may must后接完成式的用法 (1)can could后接完成式的用法 在否定式或疑问句中，表示对过去发生过的事情的怀疑或不肯定的态度。如:Could he have said so?
在肯定句中，可以表示过去可能做到而实际并没做到的事情，有劝告或责备的语气。如:--When did you answer her letter？--Only yesterday.--It's too late.You could have answered it earlier，I am sure.

马

have to的基本用法
have to和must的意义相近，只是must侧重表示说话人的主观看法，而have to则表示客观需要。如:I must study hard.
I had to give it up because of illness.