What are the primary responsibilities of a flight engineer during flight operations?

The primary responsibilities of a flight engineer revolve around the technical aspects of the aircraft's operation, making option B the correct choice. Monitoring engine and system performance is critical to ensuring the aircraft operates safely and efficiently throughout the flight. The flight engineer is responsible for overseeing a variety of systems, including engines, fuel, electrical, and hydraulic systems, providing real-time assessments and troubleshooting when necessary. Their role is crucial during various flight phases, as they help identify and resolve issues that could affect the safety and performance of the aircraft.

In contrast, managing the passenger cabin and in-flight entertainment is not within the flight engineer's purview; this falls under the responsibilities of cabin crew members. Completing pre-flight passenger briefings is also not a duty associated with flight engineers, as this task is typically handled by the flight attendants. Lastly, while coordinating with air traffic control is essential for safe flight operations, this responsibility is primarily managed by the flight crew, including the pilot and co-pilot, rather than the flight engineer. Thus, the focus of the flight engineer's duties is firmly on monitoring and maintaining aircraft systems, highlighting the significance of option B.