had better + V
结构︰主词＋had better＋原形动词
说明︰此句型意为最好；还是为好。用 had better 来执行和一个助动词一样的功能。had better have＋过去分词表最好已经之意：had best 则是以为最佳，比 had better 的意思还要强调。
You had better consult a doctor soon. 你最好快点去看医生。
The policeman said to him， Youd better come with me and tell me all about the accident.
警察对他说：你最好跟我来，并告诉我这次事故的经过。
You had better have stayed at home. 你留在家里那是最好。
Hadnt you better make a market report？ 你不认为写一份市场报告好些吗？
You had better go to the factory and have a look. 你最好到厂里去看一看。
You had best not accept the offer. 你最好是不要接纳这要求。
May you + V
结构︰May＋第二、三人称主词＋动词原形＋其它
说明︰此句型意为祝。may 此处表示祝福与愿望，多用于书面语中，口语中有时也用，但显得较庄重。本句型的特点是：may 不是在主词后面，而是摆在句子开头，使全句成倒装语序，表达出祝愿的意义。
May you recover soon！ 愿您早日康复！
May you succeed in business. 祝您生意兴隆！
May our two parties achieve even greater successes in our business.
祝我们双方在生意中取得更大的成功。
may well + V
结构︰may well + 原形动词
说明︰此句型意为理当；大可。may 是助动词，well 是副词，后接原形动词.若将 well 置于主词前面，可加强语气.
You may well find that the end of the book is better than the beginning.
你应该会发现这本书的结尾比开头好。
You may well get angry with him. 你大可对他发脾气。
She is proud of her son， and well she may. 她以儿子为傲也是应该的。
An unlimited arms race may well increase the danger of war.
无限度的武器竞赛当然会增加战争的危险性。
Since he can play many musical instruments， he may well be called a man of accomplishments. 他能演奏许多乐器，当然称得上是个多才多艺的人。
may as well + V
结构︰may as well＋原形动词
说明︰此句型意为最好；不妨。等于 had better，但语气比较委婉。
We may as well leave the table after dinner is over. 晚餐后我们不妨离开桌子。
You may as well keep it a secret. 你最好将这件事保密。
You are not （physically） strong， so you may as well take care of your health.
你的体格不壮，因此最好注意健康。
may as well as
结构︰may／might as well＋原形动词 A＋as＋原形动词 B
说明︰此句型意为与其 B 倒不如 A。相当于had better A than B。may as well as实现的可能性较大，而might as well as实现的可能性较小。
Since it is raining hard， you may as well stay here as leave.
既然雨下得这么大，你与其离开倒不如待在这儿。
You might as well throw your money into the sea as lend it to him.
你借他钱不如把钱扔到海里去。
You might as well not know a thing at all as know it only a little.
只知道一点点，不如完全不晓得。
I may as well die as marry him.我与其嫁给他，倒不如去死算了。（我若嫁给他，很可能去死。）
I might as well die as marry him.
我与其嫁给他，倒不如去死算了。（我不太可能嫁给他，也不太可能去死。）
You might as well talk to a stone as try to argue with a stubborn woman.
你与其跟一个倔女人争吵，还不如对一块石头说话。
You might as well advise me to give up my fortune as my argument.
你劝我停止辩论，倒不如劝我抛弃一切财产。
You might as well ask the tree for help as request him to reduce the price.
你与其要他减价还不如求助于一棵树。
must have V-ed
结构︰主词＋must have＋过去分词
说明︰此句型意为一定曾经。本句型是对过去之事做肯定之推测，而must＋原形动词是对目前或将来之事做推测。
Anyway， he must have eaten a lot because now he is fat.
无论如何，他一定吃了很多东西，因为现在他胖了。
You must have mistaken her for her sister. 你一定是把她误认为是她的姊妹了。
They must have left. 他们一定是离开了。
The rubbing must have worked. 搓揉一定是有效了。
They must have read the article. 他们一定读过这篇文章。
You must have seen him before. 你以前一定见过他。
He must have forgotten my name. 他一定忘了我的名字。
He must have told you about it. 他一定告诉过你这件事。
Tom must have taken your dictionary by mistake. 汤姆一定是弄错了才拿了你的字典。
The poet must have been very young when he wrote this poem.诗人写这首诗时一定非常年轻。