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问题 选择题

下列说法表示时刻的是（　　）

A．第5s末

B．前5s内

C．第5s内

D．从第3s末到第5s末

答案

A、第5秒末，在时间轴上对应的是一个点，是时刻，故A正确；

B、前5s内是从0时刻到5秒末之间，在时间轴上对应一段距离，是时间，故B错误；

C、第5s内是1s钟的时间，在时间轴上对应一段距离，指的是时间，故C错误；

D、第第3s末到第5s末，在时间轴上对应一段距离，指的是时间，故D正确．

故选：A．

单项选择题

Rapid advances in computer and communication technologies have resulted in the (58) merger of these two fields. The lines have bluned among computing, switching, and digital transmission equipment, and the same digital techniques are being used for data, voice, and image transmission. Merging and evolving technologies, coupled with increasing demands for efficient and timely collection, processing, and (59) of information, are leading to the development of (60) that transmit and process all types of data. The ultimate goal of this evolution is something its proponents-some of the most powerful forces in the computing and telecommunications industries-call the (61) .The (61) will be a worldwide public telecommunications network that will deliver a wide variety of services. The (61) will be defined by the standardization of user interfaces, and will be implemented as a set of digital switches and paths supporting a broad range of traffic types and providing (62) processing services. Inpractice, there will be multiple networks, implemented within national boundaries, but from the user’s point of view there will be a single, uniformly accessible worldwide network.

The ultimate goal of this evolution is something its proponents-some of the most powerful forces in the computing and telecommunications industries-call the （） .The （） will be a worldwide public telecommunications network that will deliver a wide variety of services. The （）will be defined by the standardization of user interfaces

A．ISDN 

B．OSI 

C．DDN 

D．DSP
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单项选择题

管道内径的等级用公称直径表示，它是管道的（）。

A、名义计算直径；

B、实际直径；

C、实际外径；

D、实际内径。
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