A.DAI intercept all ARP packets on untrusted ports
B.DAI determines the validity of an ARP packet based on the valid MAC address-to-IP address bindings stored in the DHCP Snooping database.
C.DAI is used to prevent against a DHCP Snooping attack.
D.DAI forwards all ARP packets received on a trusted interface without any checks.
E.DAI forwards all ARP packets on untrusted ports.
F.DAI determines the validity of an ARP packet based on the valid MAC address-to-IP address bindings stored in the CAM table.

A.Classifying and marking traffic should be done as close to the traffic source as possible. 
B.Classifying and marking traffic should be done at the distribution layer.
C.Traffic is classified and marked as it travels through the network.
D.If untrusted traffic enters a switch， it can be marked with a new QoS value appropriate for the policy in place.
E.The trust boundary moves depending on the type of traffic entering the network.