What is the mechanism for encapsulating data and restricting access to it in OOP?

The correct answer is encapsulation, which is a fundamental principle of object-oriented programming (OOP). Encapsulation refers to the bundling of data (attributes) and methods (functions) that operate on that data into a single unit or class. This mechanism not only organizes code into manageable sections but also restricts direct access to some of the object's components, promoting a controlled interface for interaction.

By encapsulating data, a class can hide its internal state and require all interaction to occur through well-defined methods. This safeguards the integrity of the data by preventing external code from making unintended or harmful modifications. It allows the object to control how its data is accessed and modified, often through the use of private or protected access modifiers.

In contrast, polymorphism enables methods to act differently based on the object that invokes them, and inheritance allows a class to inherit attributes and methods from another class, creating a hierarchical relationship. Abstraction focuses on exposing only the relevant details to the user while hiding the complex implementation details. While all of these concepts are important in OOP, encapsulation specifically addresses the aspect of data protection and controlled access, making it the correct choice in this context.