Answer:
A. Russian society had been less influenced by Enlightenment thought than were other European states.
Step-by-step explanation:
During the late 18th and early 19th centuries, Enlightenment ideas and principles of liberalism, democracy, and nationalism had gained widespread support and led to significant political and social changes across Europe. However, Russia was less affected by these ideas and changes, in part due to its distance from the epicenter of the Enlightenment movement, its relative isolation from Western Europe, and the influence of the conservative Russian Orthodox Church. Additionally, the Russian monarchy had long maintained an autocratic system of government that emphasized the power of the ruler and the stability of the state over individual rights and freedoms.
Furthermore, while Russia did participate in the coalition that defeated Napoleon, it was not the only European state to do so. Therefore, this alone cannot explain why Russia emerged as the leading supporter of the conservative political order established in 1815.
In contrast, options B and D provide plausible explanations for why Russia emerged as a leading supporter of conservatism in the 19th century. Under Tsar Peter the Great and his successors, Russia had indeed undertaken a program of modernization and Westernization. However, this modernization was selective and geared towards enhancing the power of the state rather than promoting liberal values. Additionally, as the largest European state in terms of land area and population, Russia had significant geopolitical influence and was able to use its resources and military power to maintain the conservative political order established in 1815.