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问题 单项选择题

ib等级的本安型仪表在正常工作状态下，以及电路中存在（）时不能点燃爆炸性气体混合物。

A、一个或两个故障

B、一个故障

C、两个故障

D、两个或三个故障

答案

参考答案：B

单项选择题

颅脑CT扫描的扫描基线不包括（）

A.听眦线

B.听眉线

C.听眶线

D.听鼻线

E.眶耳线
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单项选择题

(1) In the strength of the carrier signal is varied to represent binary 1 or 0.

(2) is a system that can map a name to an address and conversely an address to an name.

(3) is a three-way handshaking authentication protocol that it’s packets are encapsulated in the point-to-point protocol

(4) is an approach that enables an ATM Switch to behave like a LAN switch.

(5) is an guided media which is made of glass or plastic and transmits signals in the form of light.

1（）

A．ASK

B．PSK

C．FSK

D．FDM
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