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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），则噪声衰减值为（）。

A．衰减一倍

B．衰减3 dB

C．不变

D．衰减6 dB

答案

参考答案：B

解析：

对于线声源，由距离引起的噪声衰减。

选择题

国务院发布的《关于开展新型农村社会养老保险试点的指导意见》指出，我国农民在60岁后将能享受国家普惠式养老保障。这有利于(　　)

①提高农村恩格尔系数　②提高农民消费预期拉动内需

③统筹城乡协调发展　④促进农村社会的和谐与稳定

A．②③④

B．①③④

C．①②④

D．①②③
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改错题
改错题。
1. How old are your brother? He is twelve.            
         A        B                                   C 		( )______
2.  Are we classmate? Yes, we are.         
      A               B                   C 		( )______
3.  Are you friends? Yes, we're.          
       A            B                 C 		( )______
4.  Who is he? He's my cousin andy.             
                 A                     B      C 		( )______
5. They are fine friends.         
      A           B    C 		( )______
6. Amy is a girl. He's twelve.             
                  A     B       C 		( )______
7. Who's your uncle? He's a doctor.          
       A               B      C		( )______
8.  Lucy and Lily are girl. They are eleven.            
               A                B                    C 		( )______
9.  Are you a teacher?  Yes, I'm.       
      A                             B   C 		( )______
10. He is tall. He is America.               
                A    B        C 		( )______
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