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问题 单项选择题

X线的波长长短与下列有关的量是

A．管电流

B．灯丝加热电压

C．电源电压

D．X线量

E．管电压

答案

参考答案：E

解析：X线波长仅与管电压有关，管电压越高，产生的X线波长愈短。

填空题

标准体系涉及面广，对于工程项目标准体系评价，应由（）牵头组织，标准员负责实施。
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单项选择题

()in the strength of the carrier signal is varied to represent binary 1 or 0．______is a system that can map a name to an address and conversely an address to an name．______is a three-way handshaking authentication protocol that it’s packets are encapsulated in the point-to-point protocol______is an approach that enables an ATM Switch to behave like a LAN switch．______is an guided media which is made of glass or plastic and transmits signals in the form of light．

A．ASK 

B．PSK 

C．FSK

D．FDM
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