What were the main steps in aircraft production during World War 1?

The chosen response correctly identifies critical aspects of aircraft production during World War I. During this period, rapid advancements in aviation technology necessitated a streamlined and efficient approach to building aircraft to meet the demands of the war.

The assembly of wing structures was fundamental, as wings are essential for flight and require precise engineering to ensure stability and performance. Installation of engines was equally important, as the engine's power directly influenced an aircraft's speed and maneuverability—key factors in combat and reconnaissance missions. The focus on these elements reflected the urgent need for functional military aircraft rather than extensive development cycles or marketing strategies that might have been appropriate in peacetime.

Other choices, while relevant to various aspects of aviation, don't capture the immediate and practical concerns of aircraft production during a time of war. Designing and testing are certainly part of the overall aircraft development process, but in the context of World War I, the emphasis shifted heavily towards rapid production and assembly to supply the front lines. Marketing and sales were not priorities when survival and effectiveness in battle were paramount. Similarly, while research and certification are crucial in modern aviation, during WWI the focus was on quickly building effective designs rather than ensuring they met lengthy regulatory standards.