Inheritance vs. Delegation

Question

The code below shows how method m() can be reused by inheritance. How works for delegation? Thanks!

  class A{
  int m();
  }

 class B extends A{}

 B b =new B()
 b.m();

Answer 1

class B {
    int m() {
        return new A().m();
    }
}

or

class B {
    private A a = new A();
    int m() {
        return a.m();
    }
}

or

class B {
    private A a;

    public B(A a) {
        this.a = a;
    }

    int m() {
        return a.m();
    }
}