An uninterruptible power system (UPS) supplies ______.

An uninterruptible power system (UPS) is designed to provide emergency backup power to critical equipment when the primary power source fails or experiences fluctuations. This is essential for maintaining operations during power outages, ensuring that systems remain operational without interruption. A UPS typically includes a battery that kicks in when it detects a loss of incoming power, allowing devices like computers, servers, and other sensitive electronics to continue functioning.

The other options do not accurately reflect the primary purpose of a UPS. Temperature readings, pressure readings, and nuclear power fall outside the operational scope of a UPS. These functions are managed by other systems and technologies specific to their respective applications. Thus, the correct choice emphasizes the UPS's role in maintaining power during critical situations, reinforcing its importance in settings where continuous operation is necessary.