What are two reasons that duplex mismatches can be difficult to diagnose? (Choose two.)

What are two reasons that duplex mismatches can be difficult to diagnose? (Choose two.)
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.

Answer: AD