A.Loop guard can be used with root guard simultaneously on the same port on the same VLAN while UDLD cannot.
B.UDLD protects against STP failures caused by cabling problems that create one-way links.
C.Loop guard detects and protects against duplicate packets being received and transmitted on different ports.
D.UDLD protects against unidirectional cabling problems on copper and fiber media.
E.Loop guard protects against STP failures caused by problems that result in the loss of BPDUs from a designated switch port.