C:
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 of a mouse.
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 libraries to reports of missing children, online services allow users to , for example, reserve airline tickets, buy stocks, purchase goods, and communicate with other users. In exchange for the service, users usually pay a monthly membership gee. They may also pay to connect to various databases on the service or to download information.
31.Online services work by providing users with___.
A. a base of information B. dumb terminals
C. a host system D. a satellite
32.How can the users of terminals without processing capability acquire the necessary information?
A. They can simply use a keyboard or a mouse.
B. They should use a modem to maintain the host system.
C. They should connect their computer to a satellite system.
D. They can access its base through the programs on the system.
33.If you copy the online information onto your PC device, you will___.
A. save the time of connecting to the online system
B. reduce the risk of losing information
C. pay just local telephone charges
D. get local information only
34.If you want to read full-text journals online, you usually have to___.
A. seek for a large amount of information
B. be connected to various databases
C. be introduced by the local library
D. pay a monthly membership fee
35.The passage is mainly about___.
A. the payment for online services
B. the functions of online services
C. the development of online services
D. the relation between online services and the users
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