What event pushed the development of the airplane? a. the defense industry b. advertising on the radio c. the development of the car d. political pressure e. world war i?

Both answers "a" and "e" are correct here. Like most inventions that make their way into prosperity, the development of the airplane was made a priority to aid in military efforts. The Army saw an advantage in using the planes to strike enemies from above and far from the locations of their own troops. It made winning battles easier.