What is the purpose of a motorcycle helmet?

The primary purpose of a motorcycle helmet is to protect the head in case of an accident. Helmets are specifically designed to absorb impact energy during a crash, which significantly reduces the risk of severe head injuries, such as concussions or skull fractures. In various studies, it has been consistently shown that wearing a helmet can dramatically increase a rider's chances of survival and lower the severity of injuries sustained in accidents.

On the other hand, while improving aerodynamics, serving as a fashion accessory, or enhancing sound systems might be secondary factors that some riders consider when choosing a helmet, they do not represent the primary function of the helmet. Safety and protection are the core reasons for wearing a helmet, making option A the most accurate answer.