Which is an appropriate voltage-monitoring safety mechanism provided in functional-safety-compliant automotive power ICs and similar devices?

Answer: C. Use a reference voltage independent of the monitored supply, and detect not only when the supply voltage falls below the allowable range but also when it exceeds it (overvoltage)

When the microcontroller's supply voltage drops, timing is not met and it malfunctions; when it rises too high, it leads to malfunction or to degradation and destruction of devices. Therefore, voltage monitoring as a safety mechanism detects both undervoltage and overvoltage and, on an anomaly, resets the microcontroller or shuts off outputs. If the reference voltage is shared with the monitored supply, a reference shift moves the supply and the monitor in the same way and the anomaly is missed, so an independent reference is used. A typical brownout detector (BOD), which resets only when voltage drops, cannot meet this requirement on its own.