Which of the following systems benefits from risers in terms of water supply?

Risers are vertical pipes that transport water from the main supply to various levels of a building or facility. They play a crucial role in water supply systems, particularly for fire protection. Sprinkler systems specifically benefit from risers because they require a reliable and adequate water supply to operate effectively.

In a sprinkler system, the risers ensure that water is delivered at sufficient pressure and volume to activate the sprinklers when needed. This is essential for suppressing fires and minimizing damage. The design of a sprinkler system includes the strategic placement of risers to ensure that all areas of the building are adequately covered, regardless of their height.

Other systems mentioned do not rely directly on risers for water supply. Heat detection systems, alarm systems, and ventilation systems are more concerned with monitoring and responding to fire hazards but do not require the same type of water supply for their operation. Therefore, the risers' primary function in relation to water supply makes sprinkler systems the clear choice for this question.