A data dictionary is the central reference that describes:

What data elements exist (tables, fields, attributes)

Field names, data types, allowed values, formats

Definitions, descriptions, and sometimes relationships

CompTIA Data+ treats the data dictionary as a key part of data governance and documentation. It allows analysts to understand:

What data the organization has

Where it is stored

How it is structured and defined

Why the other options are incorrect:

Data destruction policy (A): Describes how and when data must be securely disposed of, not what data currently exists.

Data use document (B): Focuses on how data may or may not be used (permissions, acceptable use), not the full inventory of data elements.

Data retention policy (D): Specifies how long data is stored before archival or destruction, not a catalog of what data is possessed.

Since the question is explicitly about knowing what data an organization possesses, the correct document is the Data dictionary (C).

CompTIA Data+ Reference (concept alignment):

DA0-001 Exam Objectives – Domain: Data Governance, Quality, and Controls (documentation of data assets).

CompTIA Data+ Official Study Guide – sections on data dictionaries as tools to describe available data fields and structures.