Which of the following is NOT a requirement for bicycle safety equipment?

Bicycle safety equipment is designed to ensure the visibility and protection of cyclists on the road. The requirements typically include specific items that enhance safety during both day and night riding.

A reflector on the front, a white front lamp, and a red rear reflector are all considered essential safety items. The front reflector and white lamp enhance visibility to others on the road, while the rear reflector signals a cyclist's presence from behind. These requirements help fulfill regulations aimed at increasing the safety of cyclists, ensuring that they can be seen by motor vehicles and other pedestrians.

In contrast, while a warning bell can be a useful accessory for alerting pedestrians and other cyclists, it is not mandated by law in the same way that the other items are. Therefore, it is not recognized as a necessary safety equipment requirement for bicycles, which is why it stands out as the correct choice here.