on the alert例句

Drivers must be on the alert for traffic signals.
驾驶员必须密切注意交通信号.

They were constantly on the alert not to be taken by surprise.
他们一直处于常备不懈状态以防突然袭击.

Hearing this, I was instantly on the alert.
我一听这话, 当下就警惕起来.

• #on the alert