What is the primary purpose of wing slats?

The primary purpose of wing slats is to reduce stalling speed, making option B the correct answer. Wing slats are retractable or fixed extensions on the leading edge of the wings that alter the airflow characteristics around the wing. By extending the wing's leading edge, slats increase the camber of the wing and delay airflow separation at higher angles of attack, effectively allowing the wing to operate at a higher angle before reaching stall. This capability is essential during low-speed phases of flight, such as takeoff and landing, as it enables the aircraft to maintain controllability and stability at lower speeds.

While the other options address aspects of flight performance, they do not capture the primary function of wing slats. For instance, while slats can help improve aileron effectiveness indirectly by enhancing overall wing performance, that is not their main purpose. Similarly, although slats can contribute to better fuel efficiency under certain conditions due to improved lift-to-drag ratios, that is secondary to their primary function of stall resistance. The option indicating increased lift at high speeds can mislead, as the use of slats is most critical in low-speed operations rather than at high speeds.