Which of the following is MOST commonly used by Linux operating systems?

HFS (Hierarchical File System) is primarily used by Apple's macOS and older Mac operating systems.

NTFS (New Technology File System) is the primary file system for Microsoft Windows operating systems.

FAT32 (File Allocation Table 32) is an older file system used for compatibility across various operating systems and removable media, but it is not the primary file system for modern Linux installations due to its limitations in file size and partition size.

ext4 (Fourth Extended Filesystem) is the current default and most widely used file system for many Linux distributions due to its robustness, performance, and features. It is a journaling file system that offers improved data integrity, larger file size support, and increased directory entry limits over its predecessors.