user: Question: What circuit was used on August 21?
Columns: ['Round', 'Circuit', 'Location', 'Date', 'Pole position', 'Fastest lap', 'Winning driver', 'Winning team', 'Supporting']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Sebring International Raceway', 'Sebring, Florida', 'March 19', 'Anders Krohn', 'Anders Krohn', 'Tristan Vautier', 'Andersen Racing', 'American Le Mans Series']
SQL:

assistant: SELECT "Circuit" FROM "Table" WHERE "Date" = 'August 21';