Which statement best describes a relational database?

Introduction / Context:
Relational databases are the most widely used form of database system in modern applications. The term relational refers to the mathematical concept of a relation, which is essentially a table with rows and columns. Understanding the basic definition of a relational database helps learners distinguish it from other models such as hierarchical, network, or document databases. This question asks for the statement that best captures what a relational database is.

Given Data / Assumptions:

We are using the standard relational model based on tables, rows, and columns.
Data is organized into multiple tables, each representing an entity or a relationship.
Relationships among data items are represented by keys, especially primary keys and foreign keys.
The options mention numbers and queries, but the correct answer must fit the full relational model concept, not a very narrow or misleading description.
No specific implementation such as a particular brand of database engine is assumed.

Concept / Approach:
In the relational model, each table represents a relation. Tables have rows, called tuples, and columns, called attributes. A relational database is a collection of such tables, with relationships expressed through common attributes. For example, a Customer table and an Orders table may be related through a CustomerId column that appears in both tables. This structure allows queries to retrieve related data across tables using joins. The key phrase in a good definition is that the database consists of separate but related tables, not that it focuses on floats, integers, or simple query capability alone.

Step-by-Step Solution:
Step 1: Recall that a relational database is defined as a collection of relations, which in practice are represented as tables. Step 2: Recognize that each table holds data about a specific subject, and relationships among subjects are represented by matching key values in different tables. Step 3: Evaluate the options and identify the one that explicitly states that the database consists of separate tables of related data, which is the essence of the relational model. Step 4: Confirm that this option also implies that relationships are possible between different types of data, not just specific numeric types such as floats or integers.

Verification / Alternative check:
Consider a typical business database with tables such as Customers, Products, and Orders. Each table stores data for its subject, and keys like CustomerId and ProductId link orders to the customers who placed them and the products that were ordered. SQL queries can then join these tables to retrieve related information. This example clearly illustrates that a relational database is a set of separate tables of related data, which supports the chosen statement.

Why Other Options Are Wrong:
The option that says it retrieves data related to its queries is too vague and does not capture the structural aspect of tables and relations that define the relational model.
The options that mention relationships between floats or between integers are incorrect because a relational database is not limited to any particular numeric type and does not define itself by specific data types. It can store and relate many kinds of data, including text, dates, and numbers.

Common Pitfalls:
A common misconception is that relational means the database is based on relationships in the everyday sense, rather than on mathematical relations. Another pitfall is to confuse the relational model with any database that supports SQL, even if the internal storage is not purely relational. Understanding the core idea of tables connected by keys helps clarify what is meant by relational and avoids these confusions.

Final Answer:
A relational database is best described as a system that consists of separate tables of related data that are linked by keys.