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- One should not run about aimlessly during an alert. 空袭警报期间不可到处乱跑。
- She is always on the alert for some new calamity. 她总是保持警觉以防某种新的灾难。
- Keep on the alert; we're due for an inspection. 提防着点，轮到检查我们了。
- Be sure to be watchful or alert. 必须留神，千万要提防。
- They have put the army on the alert. 他们已使军队进入戒备状态。
- The alert leopard went up to a deer quietly. 警觉的豹子静悄悄地走近一只鹿。
- An alert listener will have noticed the error. 耳朵尖的人能听出这个错。
- He varied the transmission frequency. 他变换了无线电传送的频率。
- The district was put on red alert during a terrorist bomb scare. 这个地区在得到恐怖主义者轰炸后作了应急准备。
- A unit of frequency equal to one cycle per second. 赫兹频率的单位，等于每秒一周
- Alert to circumstances; attentive. 对周围环境敏感的; 留心的
- Troops are on the alert against any possible aggression. 军队戒备着可能的来犯。
- Fatal accidents have decreased in frequency over recent years. 近年来死亡事故发生的频率已经下降。
- The boy was alert in answering the stranger's questions. 男孩很机敏地回答了陌生人的问题。
- Although he's over eighty his mind is still remarkably alert. 他虽已年过八十，但头脑仍然十分机敏。
- We can often correlate age with frequency of illness. 年龄的大小往往与发病率有关。
- Articles in Time's Medical Section often alert readers to unsuspected ailments. 《时代》周刊医药栏目里的文章常告诫读者对自己意想不到的疾病保持警惕。
- Accidents on that highway are happening with increasing frequency. 那条高速公路上车祸发生得越来越频繁。
- The cat is alert to every sound and movement. 那只猫对任何响动都很警觉。
- Suddenly the combat alert sounded. 突然战斗警报响了。
