What Is Fault Tolerance

What is fault tolerance?

A) An exact copy of a system's information
B) The ability to get a system up and running in the event of a system crash or failure and includes restoring the information backup
C) A computer system designed that in the event a component fails, a backup component or procedure can immediately take its place with no loss of service
D) A backup operational mode in which the functions of a computer component (such as a processor, server, network, or database) is assumed by secondary system components when the primary component becomes unavailable through either failure or scheduled down time