Answer: (iii) metadata

Metadata is 'data about data': it describes the structure, origin, format, quality and other attributes of the actual data — for example a schema or table definition in a data dictionary, the data type and length of a column, a file's author and creation date, or the number of rows in a relation.

A table is only the physical structure that stores the data, and a database is an organised collection of that data — neither of them describes the data. Integration is a preprocessing step that merges data from several sources, so it is a process rather than descriptive information about data. Hence only (iii) fits.