What can annul a Clearance Card Form K?

The annulment of a Clearance Card Form K requires specific conditions, and in this context, the correct answer refers to the verbal annulment of the train. When a verbal annulment is given, it indicates a clear authority has determined the train should no longer continue as initially planned. This aligns well with the operating procedures that prioritize communication and timely information updates.

In practical terms, a verbal annulment signals to all crew members and relevant personnel that the operation concerning that specific train is no longer in effect. This can be crucial in ensuring safety and proper adherence to the railroad's operational protocols. Communication must be clear and timely to prevent any misunderstandings that could lead to operational disruptions or safety risks.

The other options involve different scenarios that may not directly apply to the annulment of a Clearance Card Form K. Changes in train orders or operational errors do not serve as direct annulments, but rather adjustments or mistakes within the operation. An authorized personnel directive usually entails a formalized control over operations, which might not be immediate or specific enough to meet the requirements for annulling a Clearance Card, particularly if the directive isn't clear about annulment of the train’s status.