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问题 单项选择题

VHF收发信机音频线路输出通常为平衡输出、600欧，外接设备时（）。

A.无需考虑音频信号正、负极性与阻抗匹配问题

B.应考虑音频信号正、负极性与阻抗匹配问题

C.无需考虑音频信号正、负极性但应考虑阻抗匹配问题

答案

参考答案：C

单项选择题

DOM is a platform-and language- (66) API that allows programs and scripts　to dynamically access and update the content, structure and style of WWW documents　(　currently, definitions for HTML and XML documents are part of the specification　).The　document can be further processed and the results of that processing can be　incorporated back into the presented  (67) .DOM is a  (68) -based API to　documents ,which requires the whole document to be represented in  (69) while　processing it .A simpler alternative to DOM is the event –based SAX, which can be　used to process very large  (70) documents that do not fit into the memory　available for processing.

66（）

A．specific　　　

B．neutral　

C．contained　　

D．related
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单项选择题

IEEE802.3的物理层协议10BASE－T规定从网卡到集线器的最大距离为( )

A．100m

B．185m

C．360m

D．500m
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