What is the cause of this issue?

A customer is troubleshooting QoS in a Cisco UCS domain due to high packet drops in the network. The customer has configured the vNIC and associated QoS policy, and changed the MTU from 1000 to 1200. Packet drops still exist.

What is the cause of this issue?
A . The MTU specified here must be greater than the MTU specified in the associated QoS system class. If this MTU value is less than the MTU value in the QoS system class, packets may be dropped during data transmission.
B . The MTU specified here must be equal to or less than the MTU specified in the associated QoS system class. If this MTU value exceeds the MTU value in the QoS system class, packets may be dropped during data transmission.
C . The MTU specified here must be less than the MTU specified in the associated QoS system policy. If this MTU value exceeds the MTU value in the QoS system policy, packets may be not be dropped during data transmission.
D . The MTU must be optimized and should be changed to fc with the CLI command set mtu fc.

Answer: B