The international system has so far been successful in protecting its basic political unit, the sovereign state. Despite inherent conflicts in the international system, the Westphalian principles of state sovereignty, equality, and non-interference have formed a basis for cooperation among states. These principles have led to the uniformity of political units, allowing states to develop and adopt norms and principles for cooperation. International organizations such as the United Nations and international norms such as “the prohibition on the alteration of state borders by force” arise from the political and legal inheritance of Westphalian principles.

Realizing that their armies had only limited power because tax resources proved so meager, European states discovered that cooperation was cheaper and a more effective way to maximize their interests. Thus, the rapid development of a central mechanism for the functioning of the international system: diplomacy.

Between 1648 and 1789, each succession war was concluded with a peace settlement following an international diplomatic congress that included all the warring parties, as noted in Table 2.1. The Peace of Utrecht put an end to the Spanish Succession Wars in 1713, for instance. At these congresses, inter-dynastic kinship also facilitated compromise rather than punishment. Congress diplomacy rarely had a transformative impact on the structure of the international system. Instead, it served to restore the status quo and confirm the international system established by the Peace of Westphalia. Both winners and losers of wars had a role to play in the construction of peace. In this period, the principle of sovereign equality provided both powerful and small states with the opportunity of equal representation within the framework of congress diplomacy. The international system based on the principles of the Peace of Westphalia prevailed and was consolidated.

As understood from the information given the correct answer is D.

On the other hand, The French Revolution constituted a major blow to the existence of the Westphalian system in many respects. First it created an anomaly at the heart of international system. The international system had been composed of states whose political systems were monarchies; the practices and norms of the international system were entirely based on aristocratic traditions and values.

So when France proclaimed itself a republic in 1793, it also undermined the political homogeneity of states within the international system.

 Moreover the new regime in France interrupted inter-dynastic relations that had formed the basis of European diplomacy. European monarchies could not establish a regular relationship with  France other than war. Why? Because the bureaucracies of monarchs had no common basis on which to establish relations with a government that did not share their aristocratic values and qualifications. Nor did the French Republic have a diplomatic alternative to war, since it had not been recognized as a legitimate political unit by other states.