on the alert

phr

• ① 注意,提防,小心<for, to-V>
  • The armed forces were on the alert.三军在警戒。
  • He was instructed to be on the alert for any indications of battle.他奉命注意任何战斗的迹象。
  • They were constantly on the alert not to be taken by surprise.他们不断地提防受到突袭。