user: Question: Which opponent has a Round of 12?
Columns: ['Quarter', 'Score', 'Club', 'Opponent', 'Year', 'Round', 'Venue']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1st', '15.4.94', 'Essendon', 'Gold Coast', '2011', '6', 'Docklands Stadium']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Round" = '12';