How to call a method from a subclass in Java

Question

What does this code return ?

public abstract class A {
        public abstract void talk();
    }

public class B extends A {
        public void talk() {
            echo "Hello !"
        }
    }

A a = new B();
    a.talk();

Accepted Answer

"Hello !".

Answer

Execution error because *talk* method of class A is abstract.

Answer

Compilation error.

Answer

An error because we can not give the type A, which is an abstract class, to a variable.

Question from the Object-oriented programming - Fundamentals test