Which two statements are true about trust boundaries？（）
- AClassifying and marking traffic should be done as close to the traffic source as possible.
- BClassifying and marking traffic should be done at the distribution layer.
- CTraffic is classified and marked as it travels through the network.
- DIf untrusted traffic enters a switch， it can be marked with a new QoS value appropriate for the policy in place.
- EThe trust boundary moves depending on the type of traffic entering the network.