One of the conditions to descent below the MDA on a circling approach is:

• A. The landing runway and an alternative landing possibility (runway) are in sight.
• B. The required visual references have been established and can be maintained
• C. The ceiling is 1500 ft or higher
• D. The horizontal Visibility is at least 5 NM and the Ceiling is 1500 ft or higher.

Answer: (B)

The key point is that descending below the MDA on a circling approach is allowed only when you have the required visual references established and can maintain them throughout the circle to land. This means you must have the runway environment or other specified cues in sight and be able to keep those references in view and use them to safely complete the circle. If you can’t establish or maintain those visual references, you must stay at or above the MDA and execute a missed approach.

The other options don’t fit because they either describe seeing specific runways or alternative options, or they rely only on weather quantities (ceiling or visibility) without guaranteeing the presence and maintenance of the necessary visual cues needed to execute the circle.