user: Question: who is the opponent on 31 Jul?
Columns: ['Date', 'Opponent', 'Venue', 'Result', 'Scorers']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['18 Jul', 'Sheffield Wednesday', 'Blundell Park , Cleethorpes', 'L 1 - 2', 'Hegarty']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Date" = '31 Jul';