user: Question: Who constructed the car in round 1 with a Chassis of 250F?
Columns: ['Entrant', 'Constructor', 'Chassis', 'Engine', 'Tyre', 'Driver', 'Rounds']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Daimler Benz AG', 'Mercedes', 'W196', 'Mercedes M196 2.5 L8', 'C', 'Juan Manuel Fangio', '1–2, 4–7']
SQL:

assistant: SELECT "Constructor" FROM "Table" WHERE "Chassis" = '250F' AND "Rounds" = '1';