Question

Which of the following is used to make an abstract class?

(a) By using virtual keyword in front of a class declaration

(b) By using an abstract keyword in front of a class declaration

(c) By declaring a virtual function in a class

(d) By declaring a pure virtual function in a class

I have been asked this question in exam.

The above asked question is from OOPs Concept in section Basics Concepts of C++ of C++

Answer 1

Right answer is (d) By declaring a pure virtual function in a class

Best explanation: Abstract class should have at least one pure virtual function. Therefore to declare an abstract class one should declare a pure virtual function in a class.