The correct answer is D) he believed that a war would give the people of Germany a strong sense of national pride.
Otto von Bismark believed that a war with France would help unify Germany because he believed that a war would give the people of Germany a strong sense of national pride.
Otto von Bismark (1815-1898) was the Prime Minister of Prussia and the first chancellor of the German Empire. He was concerned about how to unify the different people that inhabited the territory of Prussia. Ethnicity was a concern for him. So one possibility he contemplated was that a war with France would help unify Germany because he believed that a war would give the people of Germany a strong sense of national pride.
The other options of the question were a) he thought France was a threat of German unity, b) he wanted France to give up Prussia, and c) he hoped the war would encourage German people to stop adopting French customs.