Which of the following concepts allows for different classes to be treated as instances of the same class through a common interface?

A) Abstraction

B) Inheritance

C) Polymorphism

D) Encapsulation

Answer: C) Polymorphism

Explanation: Polymorphism allows different classes to be treated as instances of the same class through a common interface. This can be achieved through method overriding or method overloading, enabling a unified way to call methods without knowing the specific types of the objects at compile time.