Indeed, realism, liberalism and Marxism are the fundamental divisions which are very common in different studies. On the other hand, Shimko used the basic division of realism and liberalism and further elaborated it with the division as Machiavellianism, Grotianism and Kantianism. Moreover, approaches about post-positivism and post-modernism remained only as intellectual contentions rather than a framework for analysis to be applied to the scientific research in the field of IR. The correct option is A.