Why aren't ordinary glasses or sunglasses sufficient for eye protection while riding?

Answer: B — They do not seal out wind or dust

Ordinary glasses and sunglasses do not provide adequate eye protection while riding a motorcycle primarily because they do not create a proper seal around the eyes. When riding, especially at higher speeds, wind, dust, and debris can be extremely irritating and potentially harmful to the eyes. A good pair of motorcycle goggles or a full-face helmet with a visor is designed to fit snugly against the face, which significantly reduces the chance of wind and foreign particles entering the eye area. This enhanced protection helps prevent distractions that could lead to accidents and also shields the eyes from potential injuries caused by flying debris. Other options, while they mention aspects related to eyewear, do not address the core issue of needing protection against the environment that riders face.