To climb or descend in an airplane, the pilot does what?

To climb or descend in an airplane, the pilot primarily controls the airplane's pitch attitude by using the yoke or control stick, which directly affects the elevator. Pulling the yoke back raises the elevator, increasing the angle of attack and generating more lift, which leads to a climb. Conversely, pushing the yoke forward lowers the elevator, decreasing the angle of attack, which leads to a descent. This action directly influences the aircraft's vertical performance, whereas other options either control thrust or manage lateral stability rather than directly affecting altitude changes.

Therefore, understanding how pitch control through the elevator functions is crucial for managing climbs and descents effectively. This foundational concept in aerodynamics highlights the significance of control surfaces in regulating the aircraft's trajectory in the vertical axis.