user: Question: Who was the match against at the PRIDE 31 event?
Columns: ['Res.', 'Record', 'Opponent', 'Method', 'Event', 'Round', 'Time', 'Location']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Loss', '0-5', 'Melvin Manhoef', 'TKO (punches)', 'K-1 Premium 2007 Dynamite!!', 1.0, '1:49', 'Osaka , Japan']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Event" = 'PRIDE 31';