Answer: ঘ) Encapsulation
 Explanation:
Encapsulation in Object-Oriented Programming (OOP):

Definition: Wrapping data (attributes) and methods (functions) that operate on the data into a single unit (class) and restricting access to some of the object’s components.
Purpose: Protects object integrity by preventing unauthorized access or modification.
 
Example:
 
class BankAccount {
private:
    double balance; // cannot be accessed directly outside the class

public:
    void deposit(double amount) { balance += amount; }
    double getBalance() { return balance; }
};

balance is hidden (private) → can only be accessed via methods → encapsulation.
 
Other options are incorrect:

ক) Inheritance→→Allows a class to derive properties from another class
খ) Polymorphism→→Allows one interface, multiple forms
গ) Abstraction→→Hides implementation details but focuses on what an object does, not access control