Which of the following expansion buses are most commonly used for video cards in modern computers?

The most commonly used expansion bus for video cards in modern computers is PCI Express. This interface has largely replaced older types of buses due to its high speed and bandwidth capabilities, which are crucial for handling the substantial data throughput required by graphics cards, especially for gaming and professional graphics applications.

PCI Express, or PCIe, offers a more efficient and faster point-to-point connection, which allows for greater data transfer rates compared to older technologies. Modern GPUs utilize multiple lanes within the PCIe architecture, enhancing their performance even further. This is particularly important as new generations of video games and applications demand more graphical processing power and bandwidth.

Other options like AGP were specialized for graphics cards but have been outperformed and ultimately phased out due to their limitations in speed and technology. ISA and PCI are older standards that do not match the performance levels required for contemporary graphics processing. As a result, PCI Express stands out as the optimal choice for video cards in modern systems, making it the standard in the industry today.