In a relational database management system (RDBMS), which statement best describes the fundamental way data is represented and accessed? Choose the option that is true for relational databases used in practice.

Introduction / Context:
Relational database management systems (RDBMS) organize data using relations (commonly called tables). This model underpins widely used systems such as PostgreSQL, MySQL, SQL Server, and Oracle. Understanding how data is represented and accessed is foundational for database design and querying.

Given Data / Assumptions:

• The question targets the defining characteristic of relational databases.
• We assume standard SQL capabilities for selecting, filtering, and joining data.
• We consider typical application development using an RDBMS.

Concept / Approach:
In the relational model, a relation is a set of tuples organized as a table with rows and columns. SQL provides a declarative way to access and manipulate those tables. This approach emphasizes logical representation (tables) and set-based operations, which simplifies many common data tasks.

Step-by-Step Solution:

Verification / Alternative check:
Open any RDBMS tutorial or documentation: examples invariably show creating tables, inserting rows, and querying with SELECT. This confirms tables are the central abstraction.

Why Other Options Are Wrong:

• It is difficult to access data: SQL was created to simplify data retrieval through declarative queries.
• Complex programs for simple queries: simple tasks typically require short SQL statements.
• All of the above: incorrect because the first choice is true while the others are false.
• Unstructured files only: that describes file systems or some NoSQL stores, not relational databases.

Common Pitfalls:
Confusing the relational model with specific storage engines or thinking SQL is inherently complex. Most complexity comes from data modeling choices, not from the relational approach itself.

Final Answer:
Data is represented by tables.