Who must wear a helmet when riding a motorcycle in Missouri?

The correct answer indicates that all riders under 26 years of age must wear a helmet when riding a motorcycle in Missouri. This regulation is in place as a safety measure, recognizing that younger riders may have less experience and face a higher risk of accidents. Helmets are proven to significantly reduce the risk of head injuries in the event of a crash, hence the law aims to protect these riders who may not yet have the same level of awareness or decision-making skills as those who are older.

The age limit of 26 is specifically chosen based on findings that motorcyclists in this age group benefit from the additional protection that helmets provide. By mandating helmet use for riders under this age, Missouri aims to decrease the incidence of serious head injuries and fatalities related to motorcycle accidents.

Other options suggest different age thresholds or imply that helmet use is optional, but Missouri's laws specify a younger age group to ensure greater safety oversight for less experienced riders.