Which component of a computer system connects to its PCIe slot?

The graphics card is the component that connects to a computer's PCIe (Peripheral Component Interconnect Express) slot. The PCIe slot is specifically designed for high-speed communication with certain hardware components, primarily for expansion cards such as graphics cards, network cards, and storage controllers.

Graphics cards require substantial bandwidth to transfer data quickly, especially for tasks like gaming or 3D rendering, making the PCIe interface ideal. The design and electrical architecture of PCIe enables a rapid data pathway between the CPU and the graphics card, allowing for improved performance in graphics processing.

In contrast, a cooling fan typically connects to a motherboard header rather than utilizing the PCIe slot. Storage devices may connect through other interface standards such as SATA or NVMe but not directly via PCIe slots for typical installations. System RAM connects directly to the motherboard through its dedicated slots (DIMM slots) rather than using PCIe. Thus, the graphics card is specifically tailored to use the PCIe slot, making it the correct answer.