Task: Text Categorization
Input (English): Sebastian Cabot is credited with naming this geographical feature which was first discovered by Juan Diaz de Solis, and Cabeza de Vaca governed a territory of the same name. Its rocky western shore features notable islands such as Las Hermanas and Isla Martin Garcia, while the Tigre River empties into it at its eastern shore. Lesser known cities along this river include Carmelo and Berazategui, but the better known cities of Montevideo and Buenos Aires are also situated along this river. FTP, identify this South American river which forms an estuary as it empties into the Atlantic.
Output (English): Social Science