"on the alert" in Chinese (Simplified)
保持警惕保持警觉
Definition
随时注意危险或能迅速反应；密切关注可能的问题或威胁。
Usage Notes (Chinese (Simplified))
通常用于需要提高警惕的场合，比如安全警告。比“保持警觉”更正式，强调随时关注问题，不仅仅是防御动作。
Examples
The guards stayed on the alert all night.
警卫们整夜都**保持警惕**。
Be on the alert for any suspicious people.
对任何可疑人员都要**保持警惕**。
The police were on the alert after the robbery.
抢劫后，警察一直**保持警惕**。
You have to stay on the alert when driving late at night.
深夜开车时必须**保持警惕**。
After hearing strange noises, she was immediately on the alert.
听到奇怪的声音后，她立刻**保持警惕**。
Travelers should always be on the alert for scams in big cities.
旅客在大城市要随时**保持警惕**，防骗。