user: Question: Which circuit was held on May 7 for 1 Hour?
Columns: ['Race', 'Length', 'Class', 'Circuit', 'Date']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['24 Hours of Daytona', '24 Hours', 'All', 'Daytona International Speedway', 'February 4 February 5']
SQL:

assistant: SELECT "Circuit" FROM "Table" WHERE "Date" = 'May 7' AND "Length" = '1 Hour';