alert

一只小狗应该机警而活泼。

A young dog should be ___alert and playful.

教师需要对学生行为的突然变化保持警觉。

Teachers need to be ___alert to sudden changes in students' behaviour.

一点紧张没关系——我想它能让你在开车时保持警觉。

A little bit of tension is alright - I guess it keeps you ___alert while driving.

当局对市中心发布了炸弹警告。

The authorities issued a bomb ___alert for the city centre.

已向沿海地区发布了恶劣天气警告。

A severe weather ___alert has been announced for the coastal regions.

如果检测到任何异常活动，新的安全系统会立即向你的手机发送警报。

The new security system sends an immediate ___alert to your phone if any unusual activity is detected.