System is one in which you duplicate functions in order to improve the reliability and availability of a system.

a summary definition: a system is a set of indpendent operating systems interacting in a collection of design patterns to effect desired functions

Explanation:

a system, in computer science, is a colection of independent operating systems interacting in communcation design patterns (a game theory aspect) to optimize particular desired functions. for example in medical instrumentation, desired functions may be 1) fast reponse times in microseconds (needed in medical instrumentation) and 2) desired stable event states such as required in physiological data logging as in surface electromyography.

the save and close button

given the options, i would say your best bet is c. the modem supports up to 56 kbps, which is too low for video streaming. dial up modems use actual phone lines, which only can go up to 56 kbps as that's more than sufficient for traditional phone calls. this is also the reason why when a dial-up modem connects, you hear all those sounds. it's literally using the phone line to establish a connection.