The correct answer is B. exFAT, because exFAT (Extended File Allocation Table) is designed to provide cross-platform compatibility between Windows and macOS while supporting large files and large storage devices. When an external hard drive must be readable and writable by both operating systems without additional drivers or configuration, exFAT is the preferred choice.

According to the Quentin Docter – CompTIA A+ Complete Study Guide, exFAT was developed to overcome the limitations of FAT32, such as file size and volume size restrictions, while maintaining broad operating system support. Both Windows and macOS include native support for exFAT, making it ideal for removable storage devices.

The Travis Everett & Andrew Hutz – CompTIA A+ All-in-One Exam Guide explains that NTFS is fully supported on Windows but only has limited or read-only support on macOS by default. APFS is Apple’s proprietary filesystem and is not natively supported by Windows. XFS is a Linux filesystem and is incompatible with both Windows and macOS without third-party tools.

The Mike Meyers / Mark Soper Lab Manual reinforces that for external drives shared across platforms, exFAT offers the best balance of compatibility, performance, and simplicity.

Therefore, exFAT is the best filesystem choice, making B the correct answer.