Refer to the exhibit. Which three statements are true about trust boundaries in the campus network？ （Choose three.）（）
- A A device is trusted if it correctly classifies packets.
- B A device is trusted if it correctly declassifies packets.
- C The outermost trusted devices represent the trust boundary.
- D Classification and marking occur using 802.1ab QoS bits before reaching the trust boundary.
- E Network trust boundaries are automatically configured in IOS version 12.3 and later.
- F For scalability， classification should be done as close to the edge as possible.