Which statement about NPIV is true？（）

A. NPIV provides a means to assign multiple Fibre Channel IDs to a single N-port.
B. NPIV can be enabled on a per-VSAN basis.
C. NPIV requires a "write erase" and then reload the switch in order to come up into NPIV mode. 
D. NPIV is a Cisco proprietary feature and as such works only between two Cisco switches.
E. NPIV must not be enabled on a switch that is also running N-port virtualization.