Correct Answer: A primary key is a unique identifier for an entity.
Step 1: Understand what an ER model is. An ER model (Entity-Relationship model) is a way to represent data and its relationships in a database.
Step 2: Identify what an entity is. An entity is a thing or object in the database that we want to store information about, like a person, place, or event.
Step 3: Learn about the primary key. A primary key is a special attribute (or a set of attributes) that uniquely identifies each entity in a database.
Step 4: Recognize the importance of uniqueness. The primary key ensures that no two entities in the database have the same identifier, which helps to avoid confusion.
Step 5: Conclude that the primary key is essential for organizing and retrieving data efficiently in an ER model.
