为了实现数据终端设备之间的通信，在通信网络中必须设置交换中心，以便为需要通信的数据终

发布时间：2018-01-07 19:26 │ 来源：www.tikuol.com

题型：单项选择题

问题：

为了实现数据终端设备之间的通信，在通信网络中必须设置交换中心，以便为需要通信的数据终端建立通信链路，通信结束后再拆除链路。目前在Internet网络中使用的交换技术主要是

A．电路交换

B．报文交换

C．分组交换

D．信元交换

考点：计算机等级考试数据库技术三级数据库技术笔试

题型：单项选择题

通常情况下室外氡浓度比室内氡浓度（）。

A.高

B.无差异

C.低

D.接近

E.低很多

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筷子在水中的其他各点情形也是如此，所以我们看起来筷子浸在水中的部分好像向______折起了．

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题型：单项选择题

蓝光治疗定时更换体位是（）

A.每1小时1次

B.每3小时1次

C.每5小时1次

D.每2小时1次

E.每4小时1次

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题型：单项选择题

（）不归属措施项目清单之中。

A.预留金

B.脚手架搭拆费

C.环境保护费

D.夜间施工费

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题型：单项选择题

It may be necessary, in order that .future (51) can enjoy clean air, that more of the (52) is borne by long-term central government fund．As air pollution varies enormously from place to place and can, indeed, be very local, it may also be necessary for the central government to (53) money so that local authorities can (54) special local problems. That these can be significant was shown by the report made in 1970 (55) behalf of the London Boroughs Association. This (56) that in central London since 1958 smoke concentrations have decreased by 80 percent, whereas sunshine has increased by 70 percent and winter visibility has (57) threefold, There have been (58) in mortality and hospital admissions (59) with air pollution and in the response to it of bronchitis, as well as clear if less documented increases in plant types and bird (60) n the cities.

A．see

B．watch

C．meet

D．look

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