In several nations, rulers welcomed leaders of the Enlightenment at court and asked them to help design laws and programs to reform the system, typically to build stronger national states. These rulers are called "enlightened despots" by historians. They included Frederick the Great of Prussia, Catherine the Great of Russia, Leopold II of Tuscany, and Joseph II of Austria. Joseph was over-enthusiastic, announcing so many reforms that had so little support that revolts broke out and his regime became a comedy of errors and nearly all his programs were reversed. Senior ministers Pombal in Portugal and Struensee in Denmark also governed according to Enlightenment ideals. In Poland, the model constitution of 1791 expressed Enlightenment ideals, but was in effect for only one year as the nation was partitioned among its neighbors. More enduring were the cultural achievements, which created a nationalist spirit in Poland.
Try to answer this question if possible (otherwise reply "unanswerable"): In what country was the model constitution of 1791 in effect for only one year?
Poland