adj.注意的；警惕的；不眠的；醒的
You must be watchful of your health. 你必须注意你的健康。
They were not very watchful of the traffic lights. 他们并不很注意红绿灯。
We should be watchful of computer viruses. 我们应该警惕计算机病毒。
n.警觉性；慎重
