What is the name of the production company that made the most movies?
name of the production company refers to company_name; most movies refers to max(count(company_name))
SELECT T1.company_name FROM production_company AS T1 INNER JOIN movie_company AS T2 ON T1.company_id = T2.company_id GROUP BY T1.company_id ORDER BY COUNT(T2.movie_id) DESC LIMIT 1