Refer to the exhibit. What is the effect on the trust boundary of configuring the command mls qos trust  cos on the switch port that is connected to the IP phone？（）

• A、 Effectively the trust boundary has been moved to the IP phone.
• B、 The host is now establishing the CoS value and has effectively become the trust boundary. 
• C、 The switch is rewriting packets it receives from the IP phone and determining the CoS value.  
• D、 The switch will no longer tag incoming voice packets and will trust the distribution layer switch to set theCoS
• E、 RTP will be used to negotiate a CoS value based upon bandwidth utilization on the link.