在红灯前停下车是交通规则。

Stopping at the ___red light is a traffic rule.

老板的皱眉对我来说是个明显的停止信号。

The boss's frown was a clear ___red light for me.

很多游客喜欢探索东京著名的红灯区。

Many tourists enjoy exploring the famous ___red-light district in Tokyo.