Which control surface helps to change the angle of attack during flight?

The control surface that helps to change the angle of attack during flight is the flap. Flaps are located on the trailing edge of the wings and can be extended or retracted during flight. When flaps are extended, they increase the wing's curvature and surface area, which effectively increases lift at lower airspeeds. This allows the aircraft to maintain controlled flight at slower speeds, such as during takeoff and landing phases, by enhancing the angle of attack without stalling.

The other control surfaces mentioned serve different purposes. Ailerons are primarily used for roll control and affect the wing's lift distribution on either side of the aircraft, but they do not significantly change the angle of attack of the entire wing. Slats are devices that can also enhance lift at high angles of attack but work by changing airflow over the wing rather than directly adjusting the angle of attack like flaps do. The elevator is primarily responsible for controlling pitch, which affects the angle of attack of the entire aircraft but does not alter the wing's lift characteristics as flaps do.