The most accurate response to the question regarding the role of the Franco-Prussian War in uniting Germany is:
The Franco-Prussian War convinced German states to unite under one nation-state.
This war (1870-1871) played a crucial role in facilitating the unification of Germany as it fostered a sense of nationalism among the various German states and united them against a common enemy, France. Following the victory, the German Empire was proclaimed in 1871, solidifying this unification.