Which Cisco IOS traffic-shaping mechanism statement is true？ （）

• A、class-based policing is configured using the Modular QoS command-line （MQC）
• B、only the Frame Relay traffic-shaping （FRTS） mechanism can interact with a Frame Relay network， adapting to indications of Layer2 congestion in the WAN links
• C、Distributed Traffic Shaping （DTS） is configured with the police command under the policy map configuration
• D、both Frame Relay traffic shaping （FRTS） and virtual IP （VIP）-based Distributed Traffic Shaping （DTS） have the ability to mark traffic