In object-oriented programming, what type of polymorphism is achieved at runtime? 

Method Overriding is an example of runtime polymorphism. It occurs when a subclass provides a specific implementation of a method that is already defined in its superclass. At runtime, the method that gets executed depends on the object type (the subclass instance), not the reference type (the superclass reference), thus achieving polymorphism. This allows for flexibility in code, as the same method can behave differently depending on the object calling it. Why Other Options are Incorrect: A) Method Overloading: This is an example of compile-time polymorphism, not runtime polymorphism. C) Operator Overloading: While it is a form of polymorphism, it is resolved at compile time and is not applicable to runtime polymorphism. D) Constructor Overloading: Constructor overloading is a type of compile-time polymorphism, as the constructor to be invoked is determined at compile time. E) Function Overloading: Similar to method overloading, this is also resolved at compile time, not at runtime.