Which of the following items is essential to have on hand for safe ATV riding?

Having a DOT-compliant helmet is essential for safe ATV riding because it plays a crucial role in protecting the rider's head in the event of an accident or fall. Helmets that meet Department of Transportation (DOT) standards are designed to absorb impact and reduce the risk of serious head injuries. Ensuring that a helmet fits well and is securely fastened increases its effectiveness in protecting the rider.

While items like a cell phone, first aid kit, and water are important for various aspects of safety and preparedness, they do not provide the same level of direct protection as a helmet. A cell phone can be useful for communication in emergencies, and a first aid kit can assist in providing care for injuries, while hydration is essential for overall health and stamina during rides. However, the foremost priority on an ATV is to ensure the safety of the rider, making a DOT-compliant helmet the most critical item to have on hand.