What is required to be worn around the waist during hours of darkness?

Wearing a reflective belt around the waist during hours of darkness is crucial for visibility and safety. The reflective material significantly enhances the wearer's presence in low-light conditions, making them easily seen by others. This is particularly important in military and training environments, where participants may be moving in close quarters or near vehicles. The reflective belt ensures that individuals can be identified and accounted for, reducing the risk of accidents or incidents during training or operational activities.

The other options, while they may serve other purposes, do not specifically address the need for increased visibility in low-light environments. For instance, a hydration pack is more about carrying water than visibility, while a lightweight jacket may provide warmth but does not enhance safety in the dark. A combat belt, typically used for carrying gear and equipment, is also not designed to improve visibility and may not be visible in dim lighting. Thus, the reflective belt is specifically required for safety during hours of darkness.