究竟can't have done与could't have done有什麼分别?有些人说是现在与过去的分别.有些人说是可能些较大和较小的分别.究竟是哪个才对?对不起,打错字了,是可能性。不是可能些。

来源：学生作业帮助网编辑：作业帮时间：2024/05/05 00:45:07

究竟can't have done与could't have done有什麼分别?有些人说是现在与过去的分别.有些人说是可能些较大和较小的分别.究竟是哪个才对?对不起,打错字了,是可能性。不是可能些。
究竟can't have done与could't have done有什麼分别?
有些人说是现在与过去的分别.
有些人说是可能些较大和较小的分别.
究竟是哪个才对?
对不起,打错字了,是可能性。不是可能些。

究竟can't have done与could't have done有什麼分别?有些人说是现在与过去的分别.有些人说是可能些较大和较小的分别.究竟是哪个才对?对不起,打错字了,是可能性。不是可能些。
I can't have done it without you
I couldn't have done it without you
第一位口语
第二比较书面的
意思是一模一样
你要是没有帮助我的话,我就无法完成（某事）

can't与couldn't确实有时态上的区别，但在这个结构中“情态动词+have+过去分词”，没有时态区别，因为此结构本身就已经是表示过去的了，所区别的就是后者语气更加客气和可能性更小了。

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can现在，could过去（如果指现在可以表示委婉的口气）
现在与过去的分别；可能性较大和较小的分别---都对
1 如果不是用于虚拟语气，即，不是讨论与实际情况相反的情形，而是表示推测，可以用could/might/can/may/ must (可能性由小到大）)+ 动词原形/ 动词完成式(have done表示已经完成); must这个意义时不能用于否定，否定用can't）））
He left only 10 minutes ago. He can't /couldn't have arrived there by now. 则，差别在于can't可能性更小，couldn't更大/更委婉--他10分钟前才离开，现在绝对不可能/不太可能已经到达那儿了。
2 表示对已经发生的事情做与事实相反的推测，则只能用could/might
1楼错，只能说I couldn't have done it without you.多亏了你，不然，我不可能完成。
不能用can，因为我已经做了，是在你的帮助下做的，要假设没有你的帮助，必须用could have done，不能用can/may等现在形式。
如果还没有做，就可以用can，但是不会用完成形式： I can't do it without you. 没有你，我无法做。

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