Under what condition can a serial killer be allowed on board as a prisoner?

The correct answer encompasses two important conditions: the requirement for an escorting officer and the need to ensure that there is no risk to others on board.

When a serial killer, or any high-risk prisoner, is being transported on an aircraft, safety and security are paramount. The presence of an escorting officer ensures that the prisoner is closely monitored and managed throughout the flight, preventing any potential incidents that could arise from their presence. This helps both the crew and the other passengers feel secure.

Additionally, assessing the risk to others is crucial. It is imperative that any prisoner allowed on board does not pose a threat to the crew or passengers. This consideration is not just a procedural formality; it reflects the airline's commitment to maintaining a safe environment for everyone on the flight.

Therefore, having an escorting officer in place, along with a thorough risk assessment, is critical when considering the acceptance of a serial killer as a prisoner on board. Both factors ensure the situation is handled safely and responsibly, justifying the choice of D as the correct answer.