正解:A
The appropriate power supply specification for the described workstation setup is 12V, 500W output. This specification ensures that the power supply can handle the combined power requirements of an ATX motherboard, multi-core processor, dedicated graphics solution, SATA hard drive, and DDR4 memory. The 12V rail is crucial for components such as the CPU and graphics card, while a 500W output provides sufficient power overhead to support the system under load, as well as potential future upgrades or additional components.