虽然我们的手机可以发送信号，也可以接收信号，但是没有天线的。
A. 对
B. 错
遵循802.11协议规范无线局域网使用CSMA/CD协议解决信道争用问题。( )
A. 对
B. 错
8[音频]
A. It boasts a fairly long history.
B. It produces construction materials.
C. It has 75 offices around the world.
D. It has over 50 business partners.
9
A. It has about 50 employees.
B. It was started by his father.
C. It is a family business.
D. It is over 100 years old.
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