What is one of the requirements for a participant's safety?

Wearing a helmet is a crucial safety requirement for horseback riding participants because it provides protection against head injuries in case of falls or accidents. Helmets designed for equestrian activities are specifically made to absorb impact and reduce the risk of severe head trauma. The guidelines for riding often emphasize the importance of this safety gear, as riding carries inherent risks due to the nature of working with large animals and the potential for unexpected events.

The other options may contribute to overall safety and responsible riding practices but do not have the same fundamental importance as wearing a helmet. For example, while maintaining eye contact with the instructor can enhance communication, it does not directly ensure safety in the same way a helmet does. Similarly, limiting activities to only riding and actively participating in horse care are beneficial habits but do not fundamentally address immediate safety risks associated with riding. Thus, the requirement to always wear a helmet stands out as the most vital measure for participant safety in horseback riding.