Final answer:
The Unix File System is a hierarchical file system that uses directories to organize files, with the capability of directories to be nested within each other. While influential, it is not directly a part of most major operating systems, as each has its own file system, though many are inspired by Unix.
Step-by-step explanation:
The Unix File System was released over 50 years ago and several statements about it are true. Notably, the Unix File System is indeed a hierarchical file system (c), which means that files and directories are organized in a manner that resembles a tree. This system allows users to navigate from the root directory to any subdirectory or file within the system using a path.
Furthermore, it uses directories (also commonly referred to as folders) to hold and organize files (a), and these directories can indeed be nested, meaning folders can be placed inside one another for organized storage (d).
Whilst the Unix File System has been highly influential, the notion that it is a part of most major operating systems (b) is not entirely accurate. While UNIX-based systems and those inspired by UNIX, such as Linux and macOS, use a file system that is a direct descendant or modeled after the Unix File System, other major operating systems like Windows use different file systems (e.g., NTFS, FAT32), although they have similar hierarchical structures.