Which of the following forces is responsible for pulling an airplane toward the earth?

The force that is responsible for pulling an airplane toward the earth is weight. Weight is the gravitational force acting on the mass of the airplane, causing it to be pulled downward. This force is a result of the Earth’s gravity acting on the aircraft's mass and is a critical factor in flight dynamics.

When analyzing how weight affects an airplane, it's essential to understand that it counteracts lift, the upward force generated by the wings as air flows over them. For an aircraft to become airborne, the lift must exceed the weight; conversely, when an airplane descends or lands, the weight becomes particularly significant as it must be managed effectively.

While thrust is the force that propels the airplane forward, and drag is the resistance created by air opposing the aircraft's motion, neither of these forces contribute to the downward pull. Lift and thrust work together to overcome weight during flight, but weight itself is the primary force acting downwards, making it the correct answer in this context.