According to Newton's Third Law, what causes lift on an airplane wing?

• A. Air is deflected downward by the wing, and the equal and opposite reaction pushes the wing upward.
• B. The wing creates a vacuum above the wing that pulls air upward.
• C. Lift is produced solely by engine thrust acting upward.
• D. Air pressure beneath the wing is higher on the top surface.

Answer: (A)

Lift comes from the wing pushing air downward. When the wing deflects air in a downward direction, it changes the air’s momentum. In response, the air pushes upward on the wing with an equal and opposite force. That upward reaction force is lift. The wing’s shape and angle of attack help create that downward deflection and the associated pressure differences, but the essential idea is the action–reaction pair: the wing acts on the air to move it downward, and the air pushes the wing upward. The other ideas don’t fit because a vacuum above the wing isn’t how lift is generated, engine thrust isn’t the primary lifting force, and while there is a pressure difference, it’s a result of the air being deflected and accelerated, not the sole cause.