Question from the Object-oriented programming - Fundamentals test

Which statement is true for the following code :

public class A {
    public void talk() {
        echo "Hello my name is A"
    }
}


public class B extends A {
    public void talk() {
        echo "Hello my name is B"
    }
}

A a;
if (random() < 0.5) {
    a = new A()
} else {
    a = new B()
}
B b = (B) a;
b.talk();