Question: What is an abstract class?

1. a class that is denoted by the class keyword (can be seen and used by any other class in the system--thus it is by default public)
2. something denoted by the abstract keyword and used system wide; if you want any program to create an object of a class you use the abstract class
3. a class that is denoted by the virtual keyword
4. a class that can be used only as base class

Answer: The correct answer of the above question is Option D:a class that can be used only as base class