Acompany is developing a new type of airplane that can take off like a helicopter. before they begin manufacturing the airplanes in a large scale, they first build a prototype. what is the main purpose of building a prototype? a: to find a market in which to sell the product b: to train factory workers about how to make the product on a large scale c: to make sure the design works as expected d: to show future customers what the product will look like?