Answer:
D. The formation of Germany
Step-by-step explanation:
The direct effect of nationalism in Europe was the formation of Germany. The unification of Germany in 1871 was a direct result of the nationalist movements in various German-speaking states that were motivated by the desire for a unified German state.
Therefore, the correct answer is D. The formation of Germany.
Option A is incorrect because the Austro-Hungarian Empire was formed through a complex series of treaties and political arrangements that were not solely driven by nationalism.
Option B is also incorrect because the creation of different languages is a result of historical, cultural, and geographical factors, and not necessarily directly related to nationalism.
Option C is also incorrect because the elimination of slavery was not a direct result of nationalism in Europe, but rather a result of social, economic, and political factors, and a complex series of historical events that unfolded over several centuries.