What part of the unmanned aircraft serves as its basic structure?

The basic structure of an unmanned aircraft is known as the fuselage. The fuselage serves as the main body that houses critical components such as the avionics, propulsion system, and payload. It provides the structural integrity necessary for the aircraft to maintain its shape during flight and supports the attachment of the wings and tail.

While wings are essential for generating lift and the tail helps with stability and control, they are not the primary structural component. The propeller, on the other hand, is a mechanism that provides thrust but does not contribute to the overall structural framework of the aircraft. Thus, the fuselage is indeed the fundamental part of an unmanned aircraft, making it the correct choice in this question.