Rifles, shotguns, and handguns primarily differ based on what feature?

Rifles, shotguns, and handguns primarily differ based on the design and characteristics of their barrels and the type of ammunition they use.

The barrel is a critical component as it influences how the firearm functions and the type of ammunition it can utilize. For example, rifles typically have long, rifled barrels designed to stabilize a bullet through spin, enhancing accuracy over longer distances. Shotguns, on the other hand, usually feature smooth barrels that accommodate shotshells, which contain multiple projectiles or a single slug designed for close-range shooting. Handguns come in various barrel lengths and designs, often suitable for specific types of ammunition like cartridges intended for self-defense or target shooting. As such, the barrel length, rifling, and ammunition type are fundamental aspects that create the distinctions between these firearm categories.

Other aspects like accuracy, range, weight, and materials may vary among different models within each category, but the primary differences stem from barrel and ammunition characteristics, making option A the correct answer.