Servers shut down due to overheating, not loss of electrical power. Although UPS units had battery life, without cooling systems (HVAC/air conditioning) running on backup power, server rooms overheated. Backup power for air-conditioning is essential in data center design. B). Door locks are unrelated to server shutdown. C). Increasing UPS capacity won't help cooling. D). IoT thermostats may monitor temperature but won't prevent overheating. References (CompTIA Network+ N10-009): Domain: Network Infrastructure - Environmental controls, power redundancy, HVAC systems.