What is the operating mode and role of a backup port on a shared LAN segment in Rapid PVST+?

What is the operating mode and role of a backup port on a shared LAN segment in Rapid PVST+?

A. learning mode and provides the shortest path toward the root bridge handling traffic away from the LAN B. blocking mode and provides an alternate path toward the designated bridge C. forwarding mode and provides the lowest-cost path to the root bridge for each VLAN D. listening mode and provides an alternate path toward the root bridge