Which two statements about root guard and loop guard are true? (Choose two.)

[answerhappygod]

Which two statements about root guard and loop guard are true? (Choose two.)

A. When loop guard is enabled, the port is transitioned to the root-inconsistent state.
B. Root guard disables an interface only when a superior BPDU is received
C. Loop guard uses its own keepalives to prevent loops by detecting failures.
D. Loop guard uses its own keepalives to determine unidirectional traffic.
E. Loop guard uses BPDU keepalives to determine unidirectional traffic.
F. Root guard should be enabled on an upstream interface