Which statement about STP port states is true?

A port in the blocking state transitions based on the Max Age timer (typically 20 seconds) if it stops receiving BPDUs, or directly to listening if it becomes a designated port, not always 30 seconds.

In Spanning Tree Protocol (STP), the Listening and Learning states are indeed transitory, occurring after the Blocking state and before the Forwarding state. Both of these states use the Forward Delay timer (typically 15 seconds) to ensure that BPDUs are exchanged and MAC addresses are learned respectively, without creating temporary loops by forwarding user data prematurely.

A port in the learning state can learn MAC addresses but cannot send or receive data frames; data forwarding is only permitted when the port transitions to the forwarding state.

A port in the blocking state receives BPDUs but does not learn MAC addresses; MAC address learning occurs in the learning and forwarding states.