The DAI feature has been implemented in the Company switched LAN.  Which three statements  are true about the dynamic ARP inspection （DAI） feature？ （）

• A、 DAI can be performed on ingress ports only.
• B、 DAI can be performed on both ingress and egress ports.
• C、 DAI is supported on access ports， trunk ports， EtherChannel ports， and private VLAN ports.  
• D、 DAI should be enabled on the root switch for particular VLANs only in order to secure the ARP  caches of hosts in the domain.
• E、 DAI should be configured on all access switch ports as untrusted and on all switch ports connected to other switches as trusted.
• F、 DAI is supported on access and trunk ports only.