Which of the following maneuvers must be demonstrated in reining?

In reining, backups are a critical maneuver that showcases the horse's ability to respond to cues while displaying precision and control. This maneuver requires the horse to move backward in a controlled manner, which is a demonstration of responsiveness to the rider's aids.

The importance of backups in reining lies in their demonstration of the horse's training and willingness to work with the rider. A well-executed backup shows that the horse is responsive, balanced, and capable of engaging its hindquarters. This is essential in reining competitions, where judges evaluate the horse and rider's performance based on accuracy and execution of specific maneuvers.

Other maneuvers, while integral to reining, might not be classified in the same context or emphasize the same qualities of responsiveness and control displayed in a backup. Flying lead changes, halts, and spins each have their place in a reining performance, but the ability to back up demonstrates the foundational training required for more complex movements, making it an essential skill in the discipline.