抢劫计划在那晚进行，但一个匿名来电者向警方通风报信。

The robbery was planned for that night, but an anonymous caller ___tipped the police ___off.

因此，我认为我应该写信给你，提前向你通风报信。

Therefore, I think I should write to you and ___tip you ___off in advance.

他决定向当局透露非法活动的信息。

He decided to ___tip ___off the authorities about the illegal activities.