Which of the following is a term for describing the shape of a wing's cross-section?

The term that describes the shape of a wing's cross-section is "Airfoil." An airfoil is specifically designed to generate lift when air flows over and under it, contributing to the overall aerodynamics of an aircraft. The design of the airfoil affects various performance characteristics, such as lift, drag, and stability.

In contrast, the other terms pertain to different aspects of wing design and performance. Wing span refers to the distance from one wingtip to the other, significantly influencing the aircraft's overall size and maneuverability. Wing loading is the ratio of the aircraft's weight to its wing area and impacts performance characteristics like takeoff, landing speed, and maneuverability. Aspect ratio is the ratio of the wing span to the average width (chord) of the wing, which also contributes to the aerodynamic efficiency of the aircraft. However, none of these terms refer to the actual shape of the wing’s cross-section like the airfoil does.