Which of the following is a form factor for storage drives?

The choice of M.2 as a form factor for storage drives is accurate. M.2 is a specification for internally mounted computer expansion cards and connectors, with a specific focus on enabling the use of solid-state drives (SSDs) and various other devices in a compact form factor. It has revolutionized how storage devices are integrated into computers, allowing for faster data transfer rates and more efficient use of space compared to traditional drive interfaces.

While PCIe (Peripheral Component Interconnect Express) is a high-speed interface standard that can be used to connect storage devices including some M.2 drives, it is not in itself a form factor. Similarly, SATA (Serial ATA) is a standard for connecting hard drives and SSDs but does not define the physical footprint of the drive. The 3.5-inch designation also refers to the size classification of traditional hard disk drives (HDDs) rather than a direct specification of the drive's interface or technology. M.2 stands out as it combines both the physical format and the ability to support advanced storage technologies.