What role does the rudder play in aircraft operation?

The rudder plays a crucial role in controlling the aircraft's yaw, which is the lateral movement around the vertical axis. Specifically, it allows the pilot to manage the left and right movement of the aircraft, effectively helping to maintain coordinated flight during turns and counteracting adverse yaw produced by aileron input. By deflecting the rudder to the left or right, it directs the aircraft's nose in the desired direction, aligning it with the turn and ensuring smooth operation.

In contrast, the other options fail to accurately represent the rudder's function. Adjusting altitude is primarily managed by the elevator, not the rudder. The engine throttle is controlled by the throttle lever in the cockpit and has no connection to the rudder. Finally, braking during landing is accomplished using wheel brakes, not the rudder, though the rudder can help maintain directional control during the landing roll.