........... is used to combine data and its associated functions under a single unit.

Question

Accepted Answer

The correct option is (2):
Encapsulation is a cornerstone of Object-Oriented Programming (OOP) and is precisely defined as the mechanism for bundling data (attributes/variables) and the methods (functions) that operate on that data into a single, self-contained unit, traditionally known as a class. This concept directly answers the question as its primary function is to create a logical container for related data and behavior. The bundling facilitates a critical feature called data hiding, where direct external access to the data is restricted, and all manipulation is channeled through the object's methods. This protective layer ensures data integrity, prevents accidental corruption, and promotes modularity by clearly separating the object's internal workings from its public interface.

The incorrect option is (1):
Inheritance is an entirely different concept in OOP, focused on defining a hierarchical "is-a" relationship between classes. The purpose of inheritance is to allow a new class (subclass) to acquire the properties and behaviors of an existing class (superclass), thereby promoting code reusability. It establishes a structure where one class derives features from another, rather than being the principle that binds data and its operating functions into a *single* logical unit. While it is a major pillar of OOP, it describes an inter-class relationship, not the inner-class structure.

The incorrect option is (3):
Association describes a relationship between two separate, independent classes. In object-oriented modeling, it represents a structural connection where one object "has a" or "uses" another object, such as a Department object being associated with an Employee object. Association is a higher-level design concept that models how different components interact, but it is not the process of defining the internal boundary and contents of a class. Therefore, it deals with the *link* between units, not the act of *combining* data and functions *within* one unit.

The incorrect option is (4):
Polymorphism, which translates to "many forms," is the OOP principle that allows a single interface to be used for a general class of actions, enabling functions to exhibit different behaviors in different contexts. It is realized through mechanisms like method overloading (multiple methods with the same name but different parameters) or method overriding (a subclass redefining a superclass method). Polymorphism deals with the *behavior* and *flexibility* of functions at a conceptual and runtime level, which is distinct from the structural act of physically uniting data and methods into a single class unit.