Definition: quick to notice and react to things around you Level: C1
一只年轻的狗应该机警而活泼。
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' behavior.
一点紧张感没关系——我想它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.
