n.音频铃
One should not run about aimlessly during an alert. 空袭警报期间不可到处乱跑。
She is always on the alert for some new calamity. 她总是保持警觉以防某种新的灾难。
Keep on the alert; we're due for an inspection. 提防着点，轮到检查我们了。
Be sure to be watchful or alert. 必须留神，千万要提防。
They have put the army on the alert. 他们已使军队进入戒备状态。
The alert leopard went up to a deer quietly. 警觉的豹子静悄悄地走近一只鹿。
