Loop guard and UniDirectional Link Detection both protect against Layer 2 STP loops. In which two ways does loop guard differ from UDLD in loop detection and prevention？ （）

• 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.