Which correctly describes how a lockstep CPU, used as a safety mechanism in automotive microcontrollers, works?

Answer: B. Two CPU cores execute the same instructions simultaneously, and their outputs are compared every clock cycle; a mismatch is reported as a fault

Lockstep is a scheme in which two identically configured CPU cores run the same program and a comparator checks their outputs against each other. If one result changes due to a bit flip from cosmic rays or a circuit fault, it is detected as a mismatch, giving high diagnostic coverage for CPU faults. Because the two cores do the same work, performance equals that of one core. Comparing two cores alone cannot tell which one is correct, so after detection the system performs a reset or a transition to a safe state.