改同义句It's better for you to wear warm clothes.（改同）You (had better wear)warm clothes.能给解释一下为什么用had

改同义句It's better for you to wear warm clothes.（改同）You (had better wear)warm clothes.能给解释一下为什么用had
改同义句
It's better for you to wear warm clothes.（改同）
You (had better wear)warm clothes.能给解释一下为什么用had

改同义句It's better for you to wear warm clothes.（改同）You (had better wear)warm clothes.能给解释一下为什么用had
had better(常简略为'd better)是一固定词组,had better"最好",用于表示对别人的劝告、建议或表示一种愿望.其用法有以下几点：
一、had better后面必须跟动词原形.
had better后跟动词原形(即不带to的不定式),构成had better do sth.句型.
这里的had不能用have来替换.如：
You'd better go to hospital at once.你最好立即去医院看病.
Tom, you'd better go there today.汤姆,你最好今天去那儿.
二、主语不论是第几人称,句子不论是什么时态,都要用had better的形式.如：
Now you(he,we) had better listen to the teacher.你(他,我们)现在最好听老师讲.
三、had better可用于的时态.
1.had better用于指现在.如：
Now you had better listen to the radio.你现在最好听收音机.
You had better be quiet.你最好安静一些.
2.had better用于指将来.如：
You had better start tomorrow.你最好明天动身.
We had better buy the more expensive one. It will last much longer and so it will be cheaper in the end.我们最好还是买贵些的,它更经久耐用,所以到头来,它还是更便宜些.
3.had better用于进行式,表示讲话人提出建议时,动作正在进行.如：
We had better be watching the TV play.我们最好现在就看到电视剧.
We had better be starting back now.我们最好现在就动身回去.
4.had better + have + V-ed可表示"本该做而没有做的事".如：
You had better have done it .如果你把那件事办妥就好了.(但实际上你没有那样做)
You had better have stayed with us .要是当时你和我们呆在一起多好啊.(实际上没有)
四、had better的否定式.如：
常用的否定形式是将否定副词not直接放在had better的后面.如：
You had better not miss the last bus.你最好不要错过末班公共汽车.
You had better not leave for Nanjing the day after tomorrow.你最好后天不要动身去南京.
注意：否定副词not绝不能放在had的后面.如：不能说：You hadn't better go.而应该说：You had better not go.
五、had better的疑问式.
had better通常不以普通疑问句的形式出现.但有时用于否定疑问句,常用Hadn't+主语+better...?结构,作为一种劝告形式,比肯定形式的语气更婉转一些.如：
Hadn't you better take an umbrella?你不认为该带一把伞吗?
Hadn't you better ask him first?你不认为该先问问他吗?
六、had better在反意疑问句中.
在反意疑问句中,疑问部分一般用"had+主语?",但有时可用"will you?"表示一种请求或建议.如：
You'd better not go out today, had you? 今天你最好不要外出,好吗?
I must stay at home this afternoon. You had better come to my house, will you?今天下午我必须留在家里,你最好来我家,好吗?
七、在祈使句中,had有时可以省略.如：
Better not do it .最好别做那事.
Better not wait for them.最好不要等他们.
八、had better的被动式.
You had better do it.->It had better be done.
You had better have done it.->It had better have been done.
九、had better在间接引语中的用法.
在直接引语变为间接引语的过程中,had better同第一人称或第三人称连用时,保持不变；had better同第二人称连用时,可以保持不变,也可用advise+宾语+不定式(宾补)来表示.如：
He said, "Ann had better hurry."->He said (that) Ann had better hurry.
He said, " I had better hurry."->He said (that) he had better hurry.
He said to me," You had better hurry." ->He said (that) I had better hurry.->He advised me to hurry.
十、had better在表示对别人劝告、建议时,不宜用于与陌生人、长辈及上级的交谈中.
对长辈说话时,最好不用had better.比较有礼貌的说法是：It might be better for you...；
It would be better for you.如：
It might be better for you to help me,Grandpa.爷爷,您最好能帮我一下.
[练习]
下列各句都有一处错误,请改正.
1.You'd better to wait for me at the school gate.
2.I have better write to him now.
3.You had not better go there.
参考答案：1.去掉to.2.have应改为had.3.将not置于better后面.

You had better wear warm clothes.
用had是习惯用法，had better 或 'd better 是书面写法。

had better do sth =It is better to do sth

had better do sth.
固定用法，最好做某事