on the alert

• The public should be on the alert during thunderstorms
  市民对雷暴必须提高警觉。
• Troops are on the alert against any possible aggression
  军队戒备着可能的来犯
• 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。
• She was always on the alert for some new calamities
  她总是保持警觉以防某种新的灾难。
• These networks are always on the alert for warning signs
  这些网络始终处于戒备状态，搜索警报迹象。
• Police warned the public to be on the alert for suspected terrorists
  警方警告群众警惕涉嫌的恐怖分子
• Police warned the public to be on the alert for suspected terrorists
  警方警告群众警惕涉嫌的恐怖分子
• On the alert system page , check
  在“警报系统”页上，选中
• Nuclear - armed bombers wer put on the alert during the crists
  核武装轰炸机在危机期间进入高度戒备状态。