This was not the only danger signal.

这不是唯一的危险信号。

A red lamp is often a danger signal.

红灯常常是危险的信号。

A red signal is often used as a danger signal.

红灯常常被当作危险的信号。

Recognize excessive jealousy or possessiveness as a danger signal.

认识到过度嫉妒或拥有是一个危险的信号。

Rapid breathing is a danger signal and you should call your doctor.

呼吸急促是个危险的征兆，该去请你的医生了。