How do wing fences enhance the performance of swept wings?

Wing fences are structures added to the upper surface of swept wings, and their primary function is to help manage airflow over the wing, particularly at high angles of attack. When a wing is swept back, the airflow tends to cause a flow separation at the wing's outer sections, which can lead to a stall. The correct choice highlights that wing fences effectively redirect airflow across the length of the wing chord.

By achieving this redirection, wing fences help maintain attached airflow along the wing, thereby stabilizing lift and reducing the overall likelihood of stall at high angles of attack. This results in enhanced control and efficiency of the aircraft during various flight maneuvers, especially during approach and landing phases.

Other options may hint at aspects of airflow dynamics but do not accurately capture the primary role of wing fences, which is to improve overall aerodynamic performance by managing airflow characteristics across the wing.