Under what circumstances could a private pilot log flight hours when flying a passenger?

A private pilot can log flight hours when flying with a passenger under specific conditions that relate directly to flight experience requirements. The correct answer, which emphasizes logging flight time when the experience is necessary for a rating, is based on the regulations that govern pilot logbooks.

In particular, pilots must document their flight time to meet privileges required for different certifications or ratings. For example, if a private pilot is flying passengers and that flight contributes towards hours needed for an additional rating (like instrument or commercial), those hours may be logged. This aspect is crucial because it aligns with the FAA's mission of ensuring that pilots gain the requisite experience necessary for higher certifications and ensures safety during operations.

The other options suggest circumstances that do not meet the regulatory requirements for logging flight time. For instance, logging every flight with passengers without any associated benefits towards ratings doesn't fulfill the regulations that dictate when pilots are allowed to log hours for future certification. Similarly, logging hours only when dual flight time occurs or when the flight is compensated by charity doesn't represent the comprehensive requirement that the logged time contribute to the pilot's experience for ratings accordingly.