451　must和have to

　must 和 have to 都作“必须”解。must 表示说话人的个人意志、主观看法或要求；have to 表示客观环境的需要，指不得已而必须做某事。must 没有过去时态和将来时态（但在间接引语中仍用must）; have to 的过去式为had to，将来式为will have to，表示将来“还得……”，今后“还有必要……”。

You must stop smoking. 你必须戒烟。（个人的主观要求 ）

You have to follow these rules. 你必须遵守这些规则。（客观环境有这种要求 ）

You must do as you're told. 你必须照被吩咐的去做。

You must never jump the queue. 你绝不该插队。

We have to wash our hands before a meal. 我们必得在饭前洗手。

He had to hurry or he'd be late. 他必须赶紧走，否则要迟到了。（迫于时间很紧 ）

You will have to do more exercises. 你还得做更多的练习。（才能把所学的知识巩固 ）

You must get up early. 你必须早起床 。（强烈的主观要求 ）

You have to get up early. 你有必要早起床 。（客观需要，比如要赶上某班车 ）

He must go there last night. （误）

He had to go there last night. （正）他昨天夜里必须去那里 。

提示

①have to的疑问式和否定式要用do, does或did，这里应把have作行为动词看待，不是表示“有”。

Do you have to do it today?（正）你非得今天做这件事吗？

Have you to do it today? （误）

You don't have to go there.（正）你不一定非得去那里。

You haven't to go there. （误）

②Do you have to...?的肯定回答和否定回答。

A：Do you have to do housework? 你必须做家务吗？

B： Yes, I do ./Yes, I have to ./Yes, I've got to . 是的，必须做。

B： No, I don't have to ./No, I haven't got to . 不，不必。