Rapid PVST+ Port State Overview
Propagation delays can occur when protocol information passes through a switched LAN. As a result, topology changes can take place at different times and at different places in a switched network. When a LAN port transitions directly from nonparticipation in the spanning tree topology to the forwarding state, it can create temporary data loops. Ports must wait for new topology information to propagate through the switched LAN before starting to forward frames.
Each LAN port on a software using Rapid PVST+ or MST exists in one of the following four states:
Blocking—The LAN port does not participate in frame forwarding.
Learning—The LAN port prepares to participate in frame forwarding.
Forwarding—The LAN port forwards frames.
Disabled—The LAN port does not participate in STP and is not forwarding frames.
D is the correct answer.
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/CLIConfigurationGuide/RPVSpanningTree.html
Rapid PVST+ Port State Overview
Propagation delays can occur when protocol information passes through a switched LAN. As a result, topology changes can take place at different times and at different places in a switched network. When a LAN port transitions directly from nonparticipation in the spanning tree topology to the forwarding state, it can create temporary data loops. Ports must wait for new topology information to propagate through the switched LAN before starting to forward frames.
Each LAN port on a software using Rapid PVST+ or MST exists in one of the following four states:
Blocking—The LAN port does not participate in frame forwarding.
Learning—The LAN port prepares to participate in frame forwarding.
Forwarding—The LAN port forwards frames.
Disabled—The LAN port does not participate in STP and is not forwarding frames.
Port States for RPVST+
Discarding
Learning
Forwarding
therefor both C and D are correct,
but i think D is meant to say Discarding
C is also valid a answer.
no its not