What is required for the use of expansion slots in a computer?

The requirement for the use of expansion slots in a computer is the motherboard. The motherboard serves as the main circuit board that houses the CPU, memory, and other critical components. It features a variety of expansion slots that allow users to add additional hardware components, such as graphics cards, sound cards, network cards, or other specialized cards.

Expansion slots enable the flexibility and scalability of a computer's capabilities. Without a motherboard, there would be no infrastructure to support and connect these additional components. While other parts, like the graphics card or power supply unit, are essential for the functioning of a computer, they do not provide the necessary slots or connections needed for expansion. The hard drive, primarily used for storage, would also not play a role in expansion capabilities. Thus, the motherboard is indeed the central component required for utilizing expansion slots.