Hearing this , i was instantly on the alert . 我一听这话，当下就警惕起来。
They must be constantly on the alert for the enemy . 他们必须随时注意敌人。
Old jolyon was on the alert at once . 老乔里恩立刻警觉起来。
Her fears had always been on the alert for an upheaval . 她日夜提心吊胆，严防突变。
The sentries were all on the alert . 哨兵们都警戒着。
Knowing that danger threatened, the sentry was on the alert . 因为知道危险势将发生，这哨兵加意戒备。
They were constantly on the alert not to be taken by surprise . 他们一直处于常备不懈状态以防突然袭击。
The armies were constantly on the alert not to be taken by surprise . 部队一直处于警戒状态以防突然袭击。
That was why he looked at the young man with a speculative frowning look, not condemning him, only wary and on the alert . 他所以要蹙着眉头，带着探索的神情望着这个年青人，对他存着戒心，而不斥责他，也就是这个道理。
Troops are on the alert against any possible aggression 军队戒备着可能的来犯。
