What is a possible cause?

Traffic drop for FCoE is experienced across a Nexus 5548 switch. What is a possible cause?
A. Server’s CNA does not support DCBX and PFC TLV was not negotiated.
B. A “no-drop” class has not been configured for FCoE.
C. The system is running with the default QOS policies.
D. The link is oversubscribed.