The device shown in the image is a computer power supply unit (PSU). The power supply is responsible for converting electrical power from an outlet into a usable form for the components of a computer, like the motherboard, hard drive, and other peripherals. It usually includes a fan, power connectors, and a power switch, as shown in the image. The other options, such as a hard drive, memory, or mouse, look entirely different and serve other specific functions in a computer system.