例句：
This would be regrettable.
这将令人遗憾。
Visitor a: Oh, it's so regrettable!
参观者A：啊，太遗憾了！
He has committed a regrettable mistake.
他犯了一个令人遗憾的错误。
What's wrong with regretting?
后悔有什么不好？
It is no use regretting the past.
后悔过去是没有用的。
He was regretting he'd called Mick now.
他现在在后悔给米克打了电话。