Which expansion slot standard is primarily used for graphics cards in modern computers?

Correct answer: PCIe (PCI Express)

Option B is correct because PCI Express (PCIe) is the current standard expansion interface for graphics cards in modern desktop computers, offering high bandwidth through multiple lanes (x16 for GPU slots) that meet the demanding data throughput requirements of contemporary GPUs. Option A, AGP (Accelerated Graphics Port), was the predecessor to PCIe and has not been used in new motherboards since the mid-2000s. Option C, PCI, is an older parallel bus standard with far lower bandwidth than PCIe and is no longer used for graphics cards. Option D, ISA (Industry Standard Architecture), is a legacy 8/16-bit bus from the 1980s and 1990s that is entirely obsolete for modern expansion cards.