Answer:
The correct answer is: Germany.
Explanation:
Alsace-Lorraine is a region now located in France. Its territory has been ceded from France to Germany, and back, and back again after several belic conflicts.
Growing nationalism was an important detonator in the disagreements and rivalries between European countries prior to WW1.
After the Franco-Prussian War in 1870, Alsace-Lorraine was annexed to Germany. When World War I broke out, France took the retrieval of Alsace-Lorraine as one of their main goals. This, of course, generated conflict with Germany as both countries took harsh actions in order to keep/gain Alsace-Lorraine.
Ultimately, after Germany lost WW1, France regained Alsace-Lorraine.
