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问题 多项选择题

同步远程复制和异步远程复制的主要区别是（）。

A.同步远程复制的RPO小于异步远程复制

B.同城之间多采用同步远程复制

C.异地阵列间容灾（>100KM）应采用异步远程复制

D.异步远程复制也需要主机获得远程镜像站点的确认信息

答案

参考答案：A, B, C

单项选择题

Visitors to this country are normally admitted for six months, but foreign students can usually stay for one year. They must (51) an educational institution, and they are required to study for a minimum of fifteen hours a week on a (52) course. Prospective students have to show that they can afford their studies, and that they have sufficient (53) resources to support themselves (54) in this country.

In order to work here the foreigner needs a work permit, (55) must be applied for by his prospective employer. The problem here is that the Department of Employment has the right to grant or (56) these permits, and there is little that can be done (57) it; it would be extremely unwise for a foreign visitor to work (58) a permit, since anyone doing so is liable to immediate deportation (驱逐出境). There are some people from the Common Market countries, who are often given (59) residence permits of up to five years. Some other people, such as doctors, foreign journalists, authors and others can work without permits, and foreign students are normally allowed to (60) part-time jobs while they are studying here.

55().

A.when 

B.what 

C.where 

D.which
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单项选择题

和通信网络相比，计算机网络最本质的功能是（）。

A、数据通信

B、资源共享

C、提高计算机的可靠性和可用性

D、分布式处理
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