Which statement best differentiates reliability, maintainability, and availability?

• A. Reliability is the probability of operating without failure for a specified period; Maintainability is the probability of restoring operation within a given time after failure; Availability is the fraction of time the system is operational.
• B. Reliability is the fraction of time the system is operational; Maintainability is the time to repair; Availability is the probability of operating without failure.
• C. Reliability is the time to failure; Maintainability is the hazard rate; Availability is the mean time between failures.
• D. Reliability is the probability of operating without failure for a specified period; Maintainability is the probability of restoring operation within a given time after failure; Availability is the fraction of time the system is operational.

Answer: (D)