Three devices used to trip preaction valves are fixed temp devices, rate devices, and ___________ devices.

The correct choice is the combination device. In a preaction sprinkler system, the three common types of devices used to trip the preaction valves include fixed temperature devices, rate devices, and combination devices.

Combination devices incorporate both fixed temperature and rate-of-rise features. This allows them to ensure activation under varying fire scenarios, providing a higher level of safety and effectiveness. The fixed temperature component reacts to heat, while the rate-of-rise component detects a rapid increase in temperature, enhancing the system's ability to respond to potential fire situations more reliably than using either of the other types alone.

Thus, combination devices play a crucial role in ensuring that preaction valves operate correctly, contributing to the overall reliability of the sprinkler system in protecting structures from fire.