Which statement is correct about the number of available QoS system classes in FCoE?

While the number of classes is hard-set, specific non-essential classes might be disabled, so stating it 'cannot be disabled' in general is too absolute.

The number of QoS system classes in FCoE is typically hard-set, not configurable with an upper limit of 16; Cisco Nexus platforms often have 8 queues/classes per port by default.

The number of QoS system classes for FCoE is hard-set on most Cisco Nexus platforms, and critically, the best-effort (default) and Fibre Channel classes cannot be disabled as they are essential for network operation and FCoE lossless transport.

While some classes might be disabled, the best-effort and Fibre Channel classes are mandatory and cannot be disabled, making the statement 'can disable all but one class' incorrect.

The number of QoS system classes in FCoE is typically hard-set to a specific value, like 8, but it is not configurable with an upper limit of eight; it's a fixed system configuration.