Final answer:
Prussia eventually unified and evolved into Germany following a surge in German nationalism post-1815 and failed revolutions aimed at unification.
Step-by-step explanation:
Prussia later evolved into the country of Germany. After the German Confederation was formed post-1815, German nationalism strengthened significantly. This nationalism led to the revolution of 1848 and, although it failed to unite Germany at the time, it set the stage for future unification. Eventually, under the leadership of Prussia rather than Austria, a unified German state emerged.
In answer to the student's question, Prussia evolved into option (d) Germany.
In the mid-19th century, Germany underwent unification and emerged as a stronger and more dominant force in Europe. Otto von Bismarck, Germany's prime minister, played a significant role in this process, forging alliances and maintaining peace in the region.