Which factors can affect the reliability and performance of sprinkler systems?

The reliability and performance of sprinkler systems can be significantly impacted by various factors, with one of the most critical being the condition and configuration of the system components. When valves are partially or completely closed, they obstruct the flow of water, reducing the efficacy of the sprinkler system during a fire. This can lead to insufficient water supply to the nozzles, rendering the system ineffective in suppressing the flames.

Additionally, poor or improper main pipe sizing can hinder water flow and pressure, impacting the overall system performance. Distribution obstructions, such as debris or blockages in the pipes or sprinkler heads, can prevent water from being delivered effectively to the intended areas, further jeopardizing the system's reliability.

In contrast, while high temperatures, water quality, and other factors mentioned in the other options can impact specific aspects of a fire protection system, the combination cited in this correct answer highlights fundamental mechanical and structural issues that directly influence the operational capability of sprinkler systems during an emergency.