Which of the following best describes the concept of 'Encapsulation' in Object$-$Oriented Programming?

a$.$ The process of inheriting the properties of one class into another class.

b$.$ A design principle where each class should have only one reason to change.

c$.$ The bundling of attributes and methods that operate on the data within one unit or class, and restricting direct access to some of an object's components.

d$.$ A technique where an object mimics another class's interface, making them interchangeable.