Which three statements are correct about the IEEE 802.3af Power over Ethernet standard? (Choose three.)

A.
It defines a port that acts as a power source to be a PSE.

B.
It defines a powered device to be a PDE.

C.
It defines how a powered device is detected.

D.
It defines three methods of delivering Power over Ethernet to the discovered powered device.

E.
It describes five power classes to which a device may belong.

F.
It defines power class 0 as being reserved for future use.