What key features are considered in the classification of aircraft?

The classification of aircraft primarily involves key structural components that define their design and functionality. The correct answer focuses on essential elements: the wings, engine, fuselage, and tail.

Wings are crucial for generating lift, which is fundamental for the flight of the aircraft. The engine provides the necessary thrust to propel the aircraft forward. The fuselage is the main body of the aircraft, housing passengers, cargo, and various systems, while the tail stabilizes the aircraft and plays a significant role in its control and maneuverability.

The other options include elements that, while important to aircraft function, do not capture the primary structural attributes used for classification. For example, in one option, the cockpit is included, which is an important area but does not contribute to the broader classification of aircraft types. Similarly, components like propellers and landing gear are significant for operation but do not define classifications in the same structural context as wings, engine, fuselage, and tail do.