问题 单项选择题

线声源的声音传播距离增加一倍(假设r/L<1/10,即可视为无限长线声源),测噪声:

A.衰减1倍
B.衰减6dB
C.不变
D.衰减3dB

答案

参考答案:D

解析:基础知识。

填空题

阅读下面的短文,用括号内所给的适当形式填空,必要时可加助动词。

      Have you ever had problems in your life and don’t know how to be happy? If so, you will find “Being

a Happy Teenager” _1___ (write) by Australian writer, Andrew Matthews, useful.

     Andrew Matthews is a ___2___  (write), cartoonist and speaker. His books __3___ (translate) into

20 languages. He has been on over 2000 ___4___ (radio) and TV programs.

     In this book, Matthews tells us how___5____ (have) a happy life and answers the questions of

teenagers.

        There are many topics such as parents and friends, and the book says we should stop ___6___ (be)

angry and forgive. The book tells us about ___7____ (use) skills such as how to put what you have

learned into pictures of your mind to make your memory better. Many teenagers think that ____8___

(happy) comes from a good exam marks or praise form other people. But you can still be happy when

there are no such “good” things.

      _____9____ (succeed) comes from a good attitude. If you learn from ___10____ (problem), you

will have success in the future.

      Some school boys have problems such as being too tall or too short. But Matthews tells us happiness

comes from ___11___ (think) about things in positive way. 

      If you are tall, people notice you and you can get a better view at the movie; if you are short, your

clothes and shoes take ___12___ (little) room in your bedroom! This is Matthews’ most important

lesson: you choose to be happy!

单项选择题