Which of the following is the major advantage of PCI-e over PCI-X?

Sensitivity to background noise is generally a characteristic of the physical signaling, not a major advantage or disadvantage that fundamentally distinguishes PCI-e over PCI-X.

The height of the card is a physical form factor specification and is not a fundamental technological advantage of PCI-e's architecture over PCI-X.

PCI-X, like traditional PCI, uses a shared bus topology where all devices on the bus contend for the same bandwidth, which is a disadvantage, not an advantage, compared to PCI-e.

PCI-e (PCI Express) utilizes a point-to-point bus topology, where each peripheral device has its own dedicated connection to the root complex. This dedicated connection eliminates the bandwidth contention issues inherent in the shared bus design of older PCI and PCI-X architectures, providing higher, more reliable throughput for each device.