When should a pilot use a PANPAN call?

A PANPAN call is an announcement made to indicate an urgent situation that requires assistance but does not pose an immediate threat to the safety of the aircraft or its occupants. This type of call is appropriate when the aircraft is experiencing issues that could escalate if not addressed promptly, yet the situation is not dire enough to warrant a distress call.

In this context, the situation described aligns perfectly with B, as it implies a need for assistance without the presence of an immediate danger. This is a crucial communication tool in aviation, ensuring that air traffic control and other relevant agencies are aware that a pilot may require help due to circumstances that don't amount to a full emergency.

The other options suggest scenarios that either involve a higher degree of urgency or different circumstances altogether. For instance, an emergency requiring immediate evacuation would classify the situation as a distress that necessitates a MAYDAY call rather than a PANPAN. Minor technical issues might not justify any call if they don't affect flight safety or operations, while choosing to return to the departure airport may not represent a situation requiring assistance, depending on the context of the return.