user: Question: Which category had a year of 1991?
Columns: ['Year', 'Category', 'Champion', 'Runner-up', 'Score']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1991.0, 'V', 'Sandra Cecchini', 'Magdalena Maleeva', '6-4, 3-6, 7-5']
SQL:

assistant: SELECT "Category" FROM "Table" WHERE "Year" = 1991.0;