而采用（）和电缆调制解调器（Cable Modem）也可获得和后者同样数量级的接入带宽。

A．HFC
B．GSM
C．CDMA
D．HDSL

向端用户提供尽可能宽的网络接入是引起人们广泛关注的技术。（）只能提供128kbit/s的接入数据速率，（）则是通过电话双绞线向端用户提供更高信息传输带宽的一种接入技术，而采用（）和电缆调制解调器（Cable Modem）也可获得和后者同样数量级的接入带宽。第3代无线通信的（）可提供高达2Mbit/s的接入数据速率。光纤到户，即（），则是将来的一种发展方向。

题目标签：数量级调制解调器电缆调制解调器

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参考解析：

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举一反三

【单选题】Online services are managed by a host system that maintains a base of information available to satellite users. Users of so-called "dumb" terminals (i. e., those without processing capability)simply a...

Online services are managed by a host system that maintains a base of information available to satellite users. Users of so-called "dumb" terminals (i. e., those without processing capability)simply access the information base via programs stored on the system. Personal computer (PC) users typically access the host through a modem (调制解调器). A PC software program serves as an interface (接口)between the server and a PC, allowing the user to operate through the online system and select different databases using a keyboard or a mouse.

B.
National and regional online systems usually have local telephone numbers that PC modems can call to access either a local information base or an indirect long-distance connection, thus reducing long-distance telephone fees. Some online systems allow users ’to copy large volumes of information onto a local memory storage device, which also reduces the time the user is connected to the online system.

Besides offering a great number of different information based, ranging from full-text journal li- braries to reports of missing children, online services allow users to, for example, reserve airline tick- ets, buy stocks, purchase goods, and communicate with other users. In exchange for the service, users usually pay a monthly membership fee. They may also pay to connect to various databases on the service or to download information.