Which statement best describes Cisco IOS Zone-Based Policy Firewall？（）

• A、A router interface can belong to multiple zones.
• B、Policy maps are used to classify traffic into different traffic classes， and class maps are used to assignaction to the traffic classes.
• C、The pass action works in only one direction
• D、A zone-pair is bidirectional because it specifies traffic flowing among the interfaces within the zone-pair in both directions.