If tank loads are out of balance, the auto balance system stops motive flow to which tank?

The correct answer is the light tank. In an aircraft's fuel management system, the auto balance system is designed to maintain an even distribution of fuel across the tanks to ensure optimal weight and balance. When tank loads are out of balance, specifically when one tank is lighter than the others, the auto balance system will stop the motive flow to the light tank.

This action helps to prevent further depleting the lighter tank while allowing fuel to continue flowing from the heavier tank(s) to the light tank. By stopping fuel flow into the lighter tank, the auto balance system ensures the overall fuel distribution is corrected effectively, thereby enhancing stability and performance during flight.

The other choices represent tanks that are either too full (heavy tank) or are not the focus during balancing (the center and aft tanks), and therefore do not receive the same priority for flow cessation in balancing the overall fuel load.