What is a primary feature of a CD-ROM?

A primary feature of a CD-ROM is that it is a readonly optical disc that is designed to store data that cannot be modified or rewritten once it has been written during the manufacturing process. This characteristic makes CD-ROMs particularly suitable for distributing software, games, and other content that should remain unchanged. The inability to rewrite data on a CD-ROM ensures the integrity and consistency of the information stored, which is especially important for archival purposes and in situations where the original data needs to be preserved exactly as it was created.

In contrast, the other options describe characteristics that do not apply to CD-ROMs. A CD-ROM cannot be easily written over or rewritten, which rules out the notion of it being writable. It also does not require Internet access for usage, as it can be accessed by a CD-ROM drive independently of any online connection. Lastly, while a CD-ROM is a physical storage device, it is not described by its size in comparison to other storage devices; rather, its most distinct feature is its readonly property.