Excercise

<<...This approach combines a large degree of protection from accidents (it’s not easy to define a new derived class by accident) with the flexibility needed for tool building using class hierarchies (you can grant yourself access to protected members by deriving a class).>>

Bjarne Stroustrup, "What is Object-Oriented Programming?"

What approach does Bjarne Stroustrup mean ?

1. Encapsulation

2. Inheritance

3. Polymorphism