The correct answer is - A. France.
The nation-state concept emerged in France, during the reign of Napoleon Bonaparte. Napoleon used this concept to consolidate France, but also to create a strong feeling of love towards the country and between the people, to make them feel special and different from the others, and that it is worth to fight for it. It worked perfectly for Napoleon since that was very fondly accepted by the people of France. This also led to the nation-state ideals to grow all over Europe very soon, which unfortunately after some time led to the emergence of nazizam.