Inheritance Hierarchy bstract Base Class> Lib Materials Books Magazine Files Rental Books Audio Books E-Books a If the root do not represent a real object, and it is only for design need we could call it Abstract Base Class( conceptual)Inheritance Hierarchy ◼ If the root do not represent a real object, and it is only for design need, we could call it Abstract Base Class (Conceptual) Lib Materials Books Magazines Files Rental Books Audio Books E-Books Abstract Base Class →