In a class, how do you refer to an instance variable using "self"?

To refer to an instance variable within a class in Python, you use the syntax 'self.variable_name'. This is because 'self' is a reference to the current instance of the class, and it is used to access variables and methods that belong to that particular object.

When you declare an instance variable inside the init method, you typically prefix it with 'self' to indicate that it is an attribute of the instance being created. For example, if you have a variable named 'age', you would declare it as 'self.age' within the init method. This makes it accessible throughout the instance methods of the class.

Using 'self.variable_name' allows you to keep track of the state and data that pertain to that specific instance of the class, enabling object-oriented programming practices like encapsulation and data hiding. Thus, this correct choice emphasizes proper syntax and the concept of instance variables in Python.