In what situation must spanning-tree be implemented?

A.
When redundant Layer 2 links, that are not part of a single EtherChannel or bundle, exist between distribution switches

B.
When redundant Layer 3 links, that are not part of a single EtherChannel or bundle, exist between distribution switches

C.
Between Distribution and Core switches when interfaces are configured with “no switchport”

D.
Between Distribution and Core switches when VSS is configured