16. Explain the syntactic rules of defining the union data type using a class object. 17. What is a nested class? How is a nested class is defined and declared in C++? 18. List the merits and demerits...

16. Explain the syntactic rules of defining the union data type using a class object.

17. What is a nested class? How is a nested class is defined and declared in C++?

18. List the merits and demerits of declaring a nested class in C++.

19. How is a pointer variable used to declare a member function of a class?

20. Explain the pointer techniques to access the member functions of a class objects.