red alert

详细解释:紧急警报

英语解释：

名词 red alert:

the highest level of alert when an attack by the enemy seems immanent (or more generally a state of alert resulting from immanent danger)

例句：

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。