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