Which flight control is used to adjust the aircraft's roll?

The ailerons are the primary flight control surfaces used to adjust an aircraft's roll. Located on the trailing edges of the wings, ailerons move symmetrically in opposite directions to create differential lift. When one aileron is deflected upward, the corresponding wing experiences a decrease in lift, while the opposite wing, with its aileron deflected downward, generates more lift. This movement causes the aircraft to roll to the side of the wing with the aileron that is moving up.

In contrast, the elevator primarily controls pitch, affecting the nose of the aircraft moving up or down, while the rudder manages yaw, influencing the side-to-side movement of the aircraft's nose. Flaps, on the other hand, are designed to increase lift during takeoff and landing, but they do not play a direct role in controlling roll. Thus, ailerons are the correct and specific controls for adjusting an aircraft's roll.