What control surface of a fixed-wing aircraft can induce a moment around the lateral axis?

The elevator is the control surface responsible for inducing a moment around the lateral axis of a fixed-wing aircraft. The lateral axis runs from wingtip to wingtip, and the elevator controls the pitch of the aircraft by changing the angle of attack of the tail. When the elevator is deflected upward, it increases the angle at which the tail pushes down, causing the nose of the aircraft to pitch up. Conversely, deflecting the elevator downward decreases the tail's angle of attack, allowing the nose to pitch down. This pitch control is essential for managing the aircraft's climb and descent, making the elevator crucial for controlling movements about the lateral axis.

In contrast, the ailerons primarily control roll about the longitudinal axis; the rudder manages yaw around the vertical axis, and the flaps are used to increase lift during takeoff and landing but do not directly induce moments around the lateral axis. Understanding the function of each control surface helps clarify why the elevator is the correct choice for this question.