Because it contains a description of its own structure, a database is considered to be ________ .

Option C: self-describing
This option is correct. A database that contains a description of its own structure is considered self-describing. This means the database schema includes metadata that describes the types of data stored, their relationships, and other structural details.

Option A: described
This option is incorrect. "Described" is a vague term and does not specifically describe the self-descriptive nature of a database.

Option B: metadata compatible
This option is incorrect. While a self-describing database includes metadata, being "metadata compatible" is not a standard term used to describe this characteristic.

Option D: an application program
This option is incorrect. A database is not an application program. It is a structured collection of data stored in a computer system that can be accessed and managed by software applications.

Conclusion:
Because it contains a description of its own structure, a database is considered self-describing, making Option C: self-describing the correct answer.