Everyone should learn something about first aid for every second will in an emergency.A.

问题补充：

Everyone should learn something about first aid，for every second will in an emergency.

A. play

B. count

C. happen

D. show

答案：

A. play

(答案→)B. count

C. happen

D. show

解析：

句意为：每个人都应该学点急救知识，因为在紧急情况下每一秒都很重要。play玩； count起关键作用；happen发生； show展示。