Which activity involves riding four-wheeled motorbikes over rough terrain?

Quad-biking involves riding four-wheeled motorbikes, commonly known as quad bikes, over rough terrain. This activity is specifically designed for off-road environments, where riders navigate through uneven landscapes, dirt tracks, and various natural obstacles. Quad bikes are distinct due to their four wheels, providing stability and control, making them ideal for such rugged terrains.

Mountain biking refers to riding bicycles on off-road trails, while ATV racing focuses on racing all-terrain vehicles which can sometimes include variations of quad bikes but is not specific to the activity of riding for leisure or exploration over rough terrain. Trail running is the activity of running on trails and does not involve any type of motor vehicle. Therefore, quad-biking is the most accurate description of the activity in question.