Inheritance and Polymorphism - General Questions

Which keyword is used to inherit from a class?

What is the output of the following program?

class A { static String s() { return "A"; } }
class B extends A { static String s() { return "B"; } }
class Main {
    public static void main(String[] args) {
        A obj = new B();
        System.out.println(obj.s());
    }
}

What is the output of the following program?

public class Main {
    public static void main(String[] args) {
        System.out.println(new B().info());
    }
}
class A { String info() { return "A"; } }
class B extends A { String info() { return super.info() + "B"; } }

What is the output of the following program?

class A { String hi() { return "A"; } }
class B extends A { String hi() { return super.hi() + "B"; } }
class Main { public static void main(String[] args) { System.out.println(new B().hi()); } }

What is the output of the following program?

public class Main {
    public static void main(String[] args) {
        A a = new B();
        System.out.println(a.x);
    }
}
class A { int x = 1; }
class B extends A { int x = 2; }