如果你发错了邮件，可以立即撤销发送。

If you send an email by mistake, you can quickly ___undo the sending.

我不得不解开这个复杂的结。

I had to ___undo the complicated knot.

他的骄傲自大最终毁掉了他的友谊。

His arrogance eventually ___undid all his friendships.