N+1 redundancy means that the infrastructure contains the number of components required to support the design load— N —plus one additional component capable of maintaining required capacity when one necessary component becomes unavailable. Consequently, A and B are correct.

Oracle documentation provides a direct example for power supplies: N represents the number of supplies required to power the fully configured system, while the additional “1” handles the load if one supply fails. This allows the system to continue operating after a single component failure. Oracle's current data-center facility guidance likewise expects resilient electrical architectures such as N+1 or 2N where appropriate.

C describes an N configuration , because only the capacity necessary for normal operation is present. Such a configuration has no spare unit to absorb a component failure.

D instead describes architecture closer to 2N , where two independent capacity sets can each support the complete required load. That provides a different and generally stronger level of redundancy.

The examination distinction is therefore: N = required capacity only; N+1 = required capacity plus one redundant unit; 2N = two independent full-capacity systems .

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