Final answer:
In computer networking, the term 'Pending' is not used to describe the status of a network port, thus it is not a valid port state. The valid port states are Open, Closed, and Blocked.
Step-by-step explanation:
When examining the choices listed for the question Which choice is NOT a valid port state? we find that the options are Open, Closed, Blocked, and Pending. Among these choices, Pending is NOT a valid port state. In the context of computer networking, the valid states for a port can be Open, indicating that the system is accepting connections, or Closed, meaning no connections are accepted. Blocked is also a valid state, where access is denied, typically due to a firewall rule. However, Pending is not commonly used as a term to describe the status of a network port; thus, it is not a valid port state.