International Relations has come to explore, examine, and embrace important concepts and theories in scholarly pursuits since its formal inception. Part of this is driven, no doubt, by the ever-increasing number and complexity of changes and challenges the world faces. Several useful frameworks have been developed to address these issues. One of them is the levels of analysis approach, particularly useful in foreign policy matters. There are three of these analytical levels: the individual level, the state-level, and the system level. The correct answer is D.