In ICT, which one of the following pairs of acronym and its expansion is incompatible?

The .rar extension actually stands for Roshal ARchive, named after its developer Eugene Roshal, so treating it as Readable ARchive is the mismatched pair.

The .gif extension correctly expands to Graphics Interchange Format, a bitmap image format that supports animation.

The .css extension correctly expands to Cascading Style Sheet, used to style web pages.

The .jpeg extension correctly expands to Joint Photographic Experts Group, a lossy image format.

RAR is a proprietary compressed-archive format offering strong compression and splitting into volumes.

File-extension expansions test whether the acronym truly names the underlying technology.