Question

Loving you is the best thing I have done 为什么have done 放在后面?

Answer 1

原因如下：
have done是现在完成时，表示动作发生在过去，一直延续到现在为止或许动作已蔽散完成滑带，或许动作还在进行。have sth.done的意思是“请/让/叫别人做某事”。
must have done sth.一定做某事。表示对过去事情的较有把握的推测，这时只能用在肯定句中，“肯定/必宏让氏须已经干过?”，在否定句和疑问句中用can't或couldn't或can/ could，例如：
1.From what you said, she must have told you all about it.
从你的话看，她一定告诉了你所有的事情。
2.The light was out. They must have gone to bed.
灯都熄了，他们必定睡了。
3.He must have done it when I was off with those assholes.
他一定是趁我和那群混蛋一起的时候做的。