maintain vigilance; be on the alert

• 保持警惕

maintain vigilance; be on the alert的用法和样例：

例句

1. But we must remain on the alert.
   但是我们现在仍然要保持警惕。
2. However, he has this aspect worry, and will maintain the vigilance.
   不过，他还是有这方面的担心，并且会保持警惕。