这次悲惨事故对所有父母来说都是一个教训。

There is a ___lesson for all parents in this tragic accident.

我父母让我还清了所有钱，这是一个我永远不会忘记的教训。

My parents made me pay back all the money, and it was a ___lesson I never forgot.

我们可以从这场灾难中学到重要的教训。

We can learn important ___lessons from this disaster.