“could +have+过去分词”的10种用法
一、表示主观猜测
即对已经发生动作或已经存在的状态作出主观上的猜测，通常可译为“可能已经…”，有时需根据具体语境来翻译。
如：
We could not have heard them because of the noise from the river.
由于有河水声我们不能听见他们的话。
Tom could have taken the money; he was here alone yesterday.
有可能是汤姆把钱拿走了，昨天他单独一个人在这里呆过。
We knew he couldn’t have paid for it, because he had no money.
我们知道不可能是他付了这笔钱，因为他没钱。
【说明】该用法也可将could换成can，但这只限于否定句和疑问句，因为can表推测时不用于肯定句，而could可以用于肯定句。
如：
Can he have left already? 他会已经离开了吗?
They can’t have gone out because the light’s on. 他们不可能出去了，因为灯还亮着。
二、表示未曾实现的能力
即表示过去本来有能力可以做某事的，但实际上没有那样去做，通常译为“本来可以、本来能够”等。
如：
The worst of it is that I could have prevented the accident.
最糟糕的是我本来可以防止这次事故的。
We could have got in for nothing—nobody was collecting tickets.
我们本可以不买票就进去—根本没人收票。
I could have passed my examination easily but I made too many stupid mistakes.
我本可以轻易通过考试，但我犯了太多不该犯的错误。
有时用于反语中。
如：
You’ve broken my pen—thanks for nothing, I could have done that for myself.
你把我的笔给弄坏了——你得了吧，就那我自己也会弄。
三、表示未曾实现的可能性
即表示过去本来可能发生的情况，而实际上没有发生，通常译为“本来可以、本来可能”
等。
如：
She could have been seriously injured. 她本来可能伤得很重的。
It’s difficult enough, but it could have been worse.
这事情够困难的了，本来可能会更糟呢。
有时也可根据语境译为“好在没有、差点”，尤其是当谈论的是“不好”的情况时。
如：She felt miserable. She could have cried. 她感到很痛苦，她差点哭了。
That was a bad place to go skiing—you could have broken your leg.
那不是一个滑雪的好地方，好在你没有把腿给摔断。
Why did you throw the bottle out of the window? Somebody could have been hurt.
你为什么把瓶子扔出窗外呢? 好在没有砸伤人。
They were lucky—they could have been killed. 他们很幸运，差点被打死了。
Did you see him fall? He could have killed himself. 你看见他摔倒了吗? 他差点摔死了。
有时需要有比较灵活的翻译：
When I discovered I’d come for the appointment on the wrong day, I could have kicked myself. 我来赴约发现把日期弄错了，感到非常懊恼。
四、表示未曾实现的想法
即表示过去本来有做某事的打算或意图，但实际上没有实现，通常译为“本来可以”。
如：
I could have lent you the money. Why didn't you ask me?
我本来可以借这笔钱给你的。
你为什么不向我提出?
I could have given you some hints, but I suppose you thought yourself too grand.
我本可以给你点提示的，但是我认为你太自负了。
五、表示未曾实现的选择
即表示过去本来可以有机会选择做某事，但实际上没有那样做，通常译为“本来可以”。
如：
Her husband could have told her, but he did not choose to.
她丈夫本来可以告诉她的，但他不想这样做。
I could have lent you the money. Why didn’t you ask me?
我本来可以借这笔钱给你的，你为什么不向我提出?
You needn’t have typed it twice. You could have used a carbon.
你没必要打两遍的，你当时本可以用复写纸打。
You needn’t have walked up; you could have taken the lift.
你没必要走着上去，你本来可以乘电梯的。
六、表示批评或责备
即表示过去本来有责任或义务应该做某事，但实际上却没有做成，含有批评和责备的意味，通常译为“本来应该”“本来可以”等。
如：
You could have started a little earlier. 你本可早点动身的。
You could have helped me—why did you just sit and watch?
你本来可以帮我一把嘛——为什么你只是坐在那儿观望呢?
I am disappointed that you didn’t tell me. You could have told me.
你没告诉我，我感到很失望，你本来应该告诉我的。
You could have let me know you were going out tonight.
你本来可以告诉我你今晚是要出去的()。
七、表示达到极限
表示即使人们尽力而为去做某事，但还是未能做成，通常用于否定句。
如：
I couldn’t have won, so I didn’t go in for the race.
反正我也赢不了，所以我就没有参加赛跑。
I couldn’t have enjoyed myself more—it was a perfect day.
我玩得没法再痛快了——这一天简直痛快极了。
八、表示惊讶
表示对所发生的情况感到惊奇，含有“竟然”的意味。
如：
It seems inconceivable that the accident could have happened so quickly.
这一事故发生得这么快，简直不可思议。
Well, I’m blown! I should never have thought you could have done it.
真想不到! 我从未想到居然办得到。
九、用于虚拟语气
在虚拟条件句中，当谈论过去的情况时，其句型通常是：主句用“could / would / should /might +have+过去分词”，从句用过去完成时。
如：
If I hadn’t warned you, you could have been killed. 我如不是警告了你，你就可能丧命了。
If you had come sooner, you could have helped us. 你如早来一点，就会帮上我们了。
If he had known the facts, he could have told us what to do.
如果他了解事实，他是可能告诉我们怎样做的。
If anybody had asked me, I could have told them what happened.
如果有谁问过我，我可以告诉他们发生了什么情况。
十、用于某些口语惯用表达
可用于某些口语惯用表达，如用于I could have sworn…，其意是“我可以发誓、我千真万确”。
如：
I could have sworn I’d paid that bill. 我可以发誓我付过账。
I could have sworn I heard a knock at the door. 我千真万确听到了敲门声。
