What was one effect of the French Revolution?

The French Revolution significantly stimulated nationalistic feelings, which is why this choice is correct. During the revolution, the emphasis on citizens' rights, popular sovereignty, and national identity created a powerful sense of nationalism not only in France but also across Europe. The ideas propagated during this period, such as liberty, equality, and fraternity, resonated with various groups and inspired them to seek their own national identities and self-governance.

This surge in nationalism fostered movements in various countries, leading to a rise in patriotic sentiments and a push for independence in nations influenced by revolutionary ideals. Examples can be seen in regions like Germany and Italy, where nationalist movements eventually emerged, seeking unity and autonomy.

While other options touch on relevant themes, they do not capture the primary effect of the revolution as accurately as the stimulation of nationalistic feelings does. The French Revolution did not result in a decrease in nationalism, the end of monarchies across Europe was not immediate or uniform, and the unification of the entire continent was not a direct outcome of the revolution itself but rather a process influenced by various factors, including nationalism and subsequent conflicts.