What does the BabyDog class demonstrate about multi-level inheritance?

class Animal {  
    void eat() { System.out.println("eating..."); }  
}  
class Dog extends Animal {  
    void bark() { System.out.println("barking..."); }  
}  
class BabyDog extends Dog {  
    void weep() { System.out.println("weeping..."); }  
}