... 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。
... may have V-ed ...
结构︰主词＋may／might have＋过去分词
说明︰此句型意为“很可能曾经…”。表示对过去之事做不太肯定的推测。而“may／might＋原形<动词>”是对现在或未来事物做推测。might have 所表示的可能性要比 may have 低一些。
He may have overslept this morning.
今天早上他或许睡过头了。
The tea is hot; he may have been here before.
茶还热着，不久前他很可能在这里。
He may have known the truth; otherwise he wouldn’t be so angry now.
他当时很可能知道事情的真相，否则他不会这么生气。
The boy might have known the truth, but I am not quite sure.
这男孩当时也许知道真相，但我不很确定。
... cannot have V-ed ...
结构︰主词＋cannot have＋过去分词
说明︰此句型意为“不可能曾经…”。是对过去之事做否定的推论，此时一定要用 cannot have 或 cannot，不能使用 must not have 或 must not。而“cannot＋原形<动词>”是对目前或将来之事做否定的推论。
She cannot have written the letter herself.
这封信不可能是她自己写的。
He is honest, so he cannot have stolen my money.
他是个老实人，所以他不可能偷了我的钱。
He cannot have caught a cold, because I saw him dancing with Mary the same day.
他不可能感冒，因为当天我还看到他跟玛丽跳舞。
... would have V-ed ...
结构︰主词＋would have＋过去分词
说明︰此句型意为“原本会…但却未如此”。用以表示“与过去事实相反”的<假设语气>。
He would have attended meeting, but upon learning that he had no time, he dropped the idea.
他原本要出席会议的，但知道没有时间，就打消了这个念头。
I would have told you the truth, but you didn’t give me a chance.
我本来要告诉你事情的真相，但是你不给我机会。
I would have done it, but I had no time.我本来要办这事的，可是没时间。
She would have married him, but when she learned that he was a rascal, she parted with him.
她本来会嫁给他的，但知道他是个流氓后，她就离开他了。
... could have V-ed ...
结构︰主词＋could have＋过去分词
说明︰此句型意为“原本能够…但却未如此”。
He could have bought the car, but soon his company went bankrupt.
他本来能买那辆车的，但没多久他的公司就倒闭了。
He could have finished it on schedule, but somehow he fell behind.
他原本能按预定进度做完这件事的，但不知怎地却落后了。
I could have done it if I had wanted to.
如果我那时想做，我能做得到的。
... should have V-ed ...
结构︰主词＋should／ought to have＋过去分词
说明︰此句型意为“原本应当…但却未如此”。此<句型>表示没有实现之过去的行为、状态，含有讲话者的责难或遗憾之意。
You should have spoken up in the meeting.
会谈时你实在应该发言（然而你却没有）。
He should at least have come to say good-by.
他至少也该来道个别（然而却没来）。
He ought to have kept his promise.
他原本应该遵守自己的诺言。
You should have been more careful in money matters.
在钱方面，你本当更小心点的。
He ought to have arrived there by now.
他现在应该已经到那里了。
The drama drew a capacity audience; you should have gone to see it.
这出戏吸引了满场观众；你真该去看的。
I should have known better
结构︰主词＋should have known better（than to＋原形动词）
说明︰此句型意为“本来不应该那样笨（而…）”，是指已经做过之事，而 know better（不致那样笨）是指未做之事。
I should have known better.
我本来不应该那样笨。
You should have known better than to talk like that.
你本应更懂事而不致说这样的话。
You should have known better than to go mountain climbing alone.
你本来不该笨得单独去爬山。
I know better than to go swimming after dinner.
我不致笨得吃过饭就去游泳。
... need not have V-ed ...
结构︰主词＋need not have＋过去分词
说明︰此句型意为“原本不必…但却…”。表示“与过去事实相反”的<假设语气>，即做了没有必要做的事。而“didn’t need to＋原形<动词>”则表示“过去的事实”，译为“当时不必…而且也没…”。need not have 在<疑问句>中表对过去之必要性的强烈疑问，即“有…的必要吗？”。
You need not have bought extra oil for this short trip.
在这么短的旅程中，你实在没有必要多买油。
You need not have got up so early.
你不必起得那么早。
Need he have gone to the station to meet her?
他有必要到车站去接她吗？
He need not have come. (But he came.)
当时他不必来。（但却来了）
He didn’t need to come. (And he didn’t come.)
当时他不必来。（而且也没来）
It was fine that day, so I need not have brought an umbrella with me.
那天天气很好，我原本不必带伞的（但却带了）。
