You have been tasked with setting a trust boundary on the Company network.  What is the basic  function of this trust boundary？（）

• A、 Trust boundaries are points in the network where Layer 2 CoS markings are converted to Layer  3 DSCP or IP precedence markings.
• B、 Trust boundaries are a point in the network where QoS functionality begins and ends.
• C、 Trust boundaries determine whether certain types of traffic can pass.
• D、 Trust boundaries are a point in the network where decisions about CoS markings on incoming  packets are made.
• E、 None of the other alternatives apply