The book, which is a useful guide for today's young people, deals with many questions and problems that face them at school and at home as well as in society.

A．are faced

B．confront

C．in opposition

D．meet

声波在介质中声衰减的术语是（）

A.传导发散

B.波幅吸收系数

C.线性比值

D.声波吸收

E.阻力指数