Which of the following allows objects to be treated as instances of their parent class, irrespective of their actual class?

Polymorphism is a fundamental concept in object-oriented programming that allows objects to be treated as instances of their parent class, regardless of their actual class. This occurs because polymorphism enables methods to be defined in a way that they can work with objects of different classes, as long as they share a common interface or superclass.

For example, if you have a parent class, say "Animal," and several subclasses, like "Dog" and "Cat," polymorphism allows you to write code that can call the same method (like "makeSound()") on both Dog and Cat objects, treating them as Animal types. This is essential for achieving flexibility and reusability in code, as it allows for dynamic method resolution at runtime.

Inheritance, while related, primarily provides the mechanism to establish a hierarchy between classes and define shared attributes and methods. Associative modeling pertains to data relationships without directly involving class hierarchies or object treatment. Abstraction is about simplifying complex systems by modeling classes that represent essential features while hiding unnecessary details but does not inherently allow for the treatment of subclasses as their parent class.

Thus, the nature of polymorphism directly aligns with the question's premise of allowing objects to behave as instances of their parent class.