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【简答题】
已知某放大器输入信号功率为2μW,输入噪声功率为0.02pW,输出信号功率为200μW,输出噪声功率为8pW。放大器输入端、输出端信噪比为(),噪声系数为()
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举一反三
【单选题】数据链路层在物理层提供比特流传输服务的基础上在通信的实体之间建立数据链路连接，传送的数据单元是
A.
比特（bit）
B.
帧（frame）
C.
分组（packet）
D.
报文（message）
【单选题】I just couldn't understand the former mayor ________ the money raised for children in poor areas.
A.
taking
B.
to take
C.
being taken
D.
to be taken
【单选题】The speaker raised his voice but still couldn’t make himself__________ ．
A.
hear
B.
to hear
C.
hearing
D.
heard
【判断题】Form 10-K must be filed with the SEC whenever a public company experiences a significant event.
A.
正确
B.
错误
【单选题】He raised his voice, ______ we still couldn’t hear anything．
A.
so
B.
or
C.
but
D.
as
【简答题】阅读理解 Some rain must fall.For many people in the world today those rainy days take the form of financial problems. If you have found yourself in such a position, you may be wondering what you should d...
【简答题】A．Each question in a form. must be answered. B．Everything in a form. must be read carefully. C．Something of your interest is most important. D．The conditions that interest you are changeable.
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