Definition: a movement, light, or sound which gives information, or tells people what to do Level: B2
老师发出信号后，孩子们都举起了旗子。
At a ___signal from their teacher, the children all held up their flags.
在我发出信号之前不要动。
Don't move until I give the ___signal.
比赛开始的信号通常是鸣枪。
The ___signal for a race to start is often the firing of a gun.
