What are reasons that duplex mismatches can be difficult to diagnose?

A.	The interface displays a connected (up/up) state even when the duplex settings are mismatched.
B.	1-Gbps interfaces are full-duplex by default.
C.	Full-duplex interfaces use CSMA/CD logic, so mismatches may be disguised by collisions.
D.	The symptoms of a duplex mismatch may be intermittent.
E.	Autonegotiation is disabled.