user: Question: Who was the opponent on April 21?
Columns: ['Game', 'Date', 'Opponent', 'Score', 'Location/Attendance', 'Record']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['72', 'April 2', 'vs Boston Celtics', 'W 109-89', 'The Omni', '41-31']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Date" = 'April 21';