put on the alert

• 处于戒备状态

put on the alert的用法和样例：

例句

1. Knowing that danger threatened, they were on the alert.
   因为知道可能会发生危险，他们处于戒备状态。
2. These networks are on the alert for warning signs that show the weakening of rock layers that can precede an earthquake.
   这些网络始终处于戒备状态，搜索地震前岩石可能松动的警告迹象。