Concept:Criterion for file classification refers to the basis on which files are grouped.
Explanation:Option A: Nature of content classifies a file as a program file or a data file. This is a standard basis.
Option B: Organizational method classifies files by the manner of arranging records, such as sequential or random access. This is also a standard basis.
Option C: Storage medium classifies files by the physical media used, for example, magnetic tape or hard disk. This is a valid basis too.
Option D: Type of data is not a recognised criterion for classifying files in WAEC Computer Studies.
Thus, the option that is not a file criterion is Type of data.
Answer:D. Type of data