When is it necessary to monitor the center tank fuel level closely?

The correct answer pertains to the monitoring of the center tank fuel level closely when fuel balance discrepancies are detected. This is crucial because the A320's fuel management system is designed to optimize weight distribution and performance. If there is a significant imbalance in fuel levels between the wings and the center tank, it can affect the aircraft's center of gravity and overall handling characteristics, potentially leading to stability issues.

Close monitoring allows for timely corrective actions, such as transferring fuel or adjusting the fuel configuration to maintain balance, thereby ensuring safe flight operations. Continuous attention to fuel balance can prevent reaching critical limits that could affect fuel flow to engines and impact the craft's performance.

The importance of monitoring the center tank closely does not primarily arise from situations occurring during climbs, the illumination of lights on the fuel control panel, or when the system is switched to manual mode; while these factors are important in their own rights, they do not directly relate to the ongoing need for managing fuel balance effectively.