Question

explain the real-word example of multilevel inheritance?

Answer 1

Suppose we have classes Animal and Mammal.
Mammal is derived from Animal
because in fact, mammal is animal.
Now suppose we add new class
Elephant.
Class Elephant is derived from Mammal because elephant is a
mammal
mammal is animal.
All these 3 classes form multilevel
inheritance:
Animal->Mammal->Elephant
because Elephant is derived
from Mammal that is derived from Animal.