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.