The fire-resistance rating of a Group R occupancy building, serving an occupant load of more than _____, must be 0.5 when it is provided with a sprinkler system.

In the context of building codes for Group R occupancy, which typically includes residential facilities like apartments or dormitories, the requirement for a fire-resistance rating is influenced by the level of risk associated with the number of occupants. When a Group R occupancy building has an occupant load of more than 10, it must have a minimum fire-resistance rating of 0.5 hours provided that a sprinkler system is installed.

This requirement recognizes that a higher occupant load presents a greater potential fire hazard and faster evacuation needs. The installation of a sprinkler system is crucial as it enhances the safety of the occupants by controlling or extinguishing fires, thus allowing for a reduced fire-resistance rating. The rating of 0.5 hours signifies that the structure is designed to withstand fire exposure for this duration, providing a balance of safety and structural integrity, especially when supplemented by active fire protection measures like sprinklers.

The other options indicate higher occupant loads but are unnecessary for the minimum fire-resistance rating of 0.5 hours with a sprinkler system, illustrating that even with a modest number of occupants, sprinklers considerably improve safety outcomes.