Final answer:
The statement is true. PC power supplies have a -12 V rail that provides voltage for serial RS-232 ports, PCI slots, and integrated LAN circuitry.
Step-by-step explanation:
The statement is true. In PC power supplies, there is indeed a -12 V rail that provides voltage for various components such as serial RS-232 ports, PCI slots, and integrated LAN circuitry. These components require a -12 V voltage supply to function properly.