user: Question: Which Opponent has a Time of 2:31?
Columns: ['Res.', 'Record', 'Opponent', 'Method', 'Event', 'Round', 'Time']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Win', '8-0', 'Mychal Clark', 'Decision (unanimous)', 'Call to Arms: Called Out Fights', 3.0, '5:00']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Time" = '2:31';