.
二、have to / have got to 的用法
1）must表示一种主观的需要,而have to 表示一种客观的需要,意思是“不得不”.如：
I have to attend an important meeting this afternoon.
今天下午我不得不参加一个重要的会议.
Mother is out,so I have to look after the shop.
妈妈不在家,因此我不得不照看商店.
2）have to 的否定形式是don’t have to,相当于needn’t.如：
They don’t have to buy a computer at present.
他们目前没有必要买电脑.
3）have to 与have got to 常可以互换.
get to do与get doing的用法区别
区别一：两者均可表示“开始做某事”,其细微区别如下.
1.get to do往往暗示一个较长的过程,含有“渐渐开始”之意,此时get后接的不定式通常为to know,to like,to hate,to understand,to realize等表示心理感觉的动词.如：
I really wanted to get to know America.我真想逐渐了解美国.
I shall get to like them in time.经过一段时间我会变得喜欢他们的.
The best way to get to know the city is to visit it on foot.要想了解这座城市,最好的方法是步行游览.
After a time you get to realize that these things don’t matter.你过些时候就知道这些事无关紧要.
注：有时也可接表示心理感觉之外的其他动词.如：
His drinking is getting to be a problem.他酗酒越来越成问题了.
He is getting to be a lovely kid.他慢慢变成一个可爱的孩子了.
You’ll get to speak English more easily as time goes by.时间一长,你的英语就会说得流利一些.
2.get doing主要用于非正式文体中,通常表示某种特定动作的开始,尤其用于get moving,get going,get thinking等搭配中.如：
We’d better get moving—it’s late.我们还是走吧——时间不早了.
They soon got talking together.他们不久就开始谈了起来.
He got to thinking that she perhaps wouldn’t come after all.他已意识到也许她根本不来了.
区别二：get to do可以表示有机会做某事或被许可做某事,但get doing没有这样的用法.如：
He never got to go to college.他从无机会上大学.
We didn’t get to see her—she was too busy.我们没有见到她——她太忙了.
When do I get to see your new baby?我什么时候能去看看你那刚出生的孩子呀?
Did you get to visit the Louvre when you were in Paris?你在巴黎的时候有机会去参观卢浮宫吗?
区别三：get to do还可以表示努力或设法做成某事,但get doing没有这样的用法.如：
At last he got to knock it down.最后他设法把它敲了下来.
Did you get to buy the tickets?你设法买到票了吗?
How did you get to be captain?你是怎样当上船长的