课本中不会教你的[M]480　must和have to

480　must和have to

◎ must和have to都作“必须”解，一般情况下可通用，美式英语中用have to较多。

You must/have to do as you are asked. 要你怎么做，你就一定要怎么做。

① must表示说话人的个人意志、主观看法或要求；或表示道义上的“必须”；have to表示“外界”的义务或客观的需要，即别人认为某事要你去做，或者有一项协议、规定、法律等，要求你必须去做。

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 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）

② 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……”。

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）

He must go there last night.

He had to go there last night.

他昨天晚上必须去那里。

He reminded me that I must be at the office by seven. 他提醒我必须在七点钟前到办公室。

③ 表示否定时，两者的含义明显不同。比较：

You have not to tell her the news. 你用不着把消息告诉她。

You must not tell her the news. 你决不可把消息告诉她。

④ have to的疑问式要用do，does 或 do 引起。

Have you to do it today？

Do you have to do it today？

你非得今天做这件事吗？

⑤ have to的否定式有两种。

You don't have to take an umbrella with you.

你不一定非得带雨伞。

You haven't to take an umbrella with you.

We don't have to go to school on Sunday. 星期天我们不上学。（通常的情况）

We haven't to go to school today，because it's Teachers' Day. 今天我们不上学，因为今天是教师节。（特定的情况）

⑥ 注意“Do 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。