Describe the key design difference between the object-oriented features of Smalltalk, Eiffel, and C++ on the one hand, and Ada, CLOS, and Fortran on the other. What are extension methods in C#? What...

Describe the key design difference between the object-oriented features of Smalltalk, Eiffel, and C++ on the one hand, and Ada, CLOS, and Fortran on the other. What are extension methods in C#? What purpose do they serve? Does a constructor allocate space for an object? Explain.