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.