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问题 单项选择题

19世纪晚期欧美工人运动重新高涨的根本原因是：（）

A.资本主义工业的飞速发展

B.各国工人人数的迅速增加

C.罢工次数增多，规模扩大

D.各国工人政党的相继建立

答案

参考答案：A

单项选择题

B2010型龙门刨床V55系统当电动机低于额定转速采用（）方式调整。

A．恒功率

B．恒转矩

C．恒力矩

D．弱磁
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单项选择题

Typically, these are concern with the establishment of (66) the network and with the control of the flow of messages across this channel. The provision of such facilities is only part of the network requirements, however, since in many applications the communicating computers may be of different types. This means that they may use different programming languages and, more importantly, different forms of (67) interface between user(application)program, normally referred to, as application processes or APs, and the underlying communication services may be (68) For example, one computer may be a small single -user computer, while another may be a large (69) system. In the earlier days of computer communication, these issues meantthat only closed communities of computers ( that is, from the same manufacturer) could communicate with each other in a meaningful way. IBM’s Systems Network.
Architecture (SNA) and DEC’s Digital Network Architecture (DNA) are just two examples of Communication software packages produced by manufacturers to allow their systems to be int erconnected together. These proprietary packages, however, of which there am still many inexistence, do not address the problem of universal interconnect ability, or open systems interconnection. In an attempt to alleviate this problem, (70) , in the late 1970s, formulated a reference model to provide a common basis ( or the coordination of standards developments and to allow existing and evolving standards activities to beplaced into perspective with one another.

A. DNAB. SNAC. the OSI D. the ISO
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