单项选择题
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
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.
A．a base of information B．dumb terminals C．a host system D．a satellite