What action must be taken regarding the cockpit voice recorder at the completion of the flight?

The action required regarding the cockpit voice recorder at the completion of the flight is to pull the circuit breaker. This is an essential procedure to ensure that the data recorded during the flight remains secured and is not unintentionally overwritten. Pulling the circuit breaker effectively safeguards the integrity of the recorded data, which is crucial for any subsequent investigations or reviews of the flight.

Turning off the cockpit voice recorder would not ensure that the data remains protected in the same way, as there might be risks of the device being unintentionally activated again. Erasing the data would compromise the valuable information that needs to be preserved for safety audits or incident investigations. Replacing the tape is not a standard procedure at the end of each flight, as the existing recording should be retained for analysis. Therefore, pulling the circuit breaker is the correct action to secure and protect the recorded information.