Final answer:
The Congress of Vienna's redrawing of Europe's borders was its most significant action, affecting nationalism by creating and restoring states, thereby fueling national consciousness and setting the stage for future conflicts. The option (A) is correct.
Step-by-step explanation:
The most important change made by the Congress of Vienna was the redrawing of national borders in Europe. After the defeat of Napoleon, who had controlled much of the continent, the Congress convened to restore balance and maintain peace. Key actions taken included Prussia and Austria adding territory, Russia absorbing part of Poland, and the reaffirmation of Swiss neutrality. While the Congress did not introduce universal suffrage, abolish monarchy, or establish a global trade network, it set the stage for future nationalist movements by reorganizing Europe's political map.
These new boundaries had significant implications for nationalism. The creation of enlarged or restored states stimulated national consciousness. For example, Greater Prussia and Austria bolstered German and Austrian nationalism respectively, while the division of Poland contributed to Polish national identity. Though these redrawn borders aimed for equilibrium, they also planted seeds for future conflicts driven by nationalist desires. Therefore, option (A) is correct.