Question: What is the favourite movie genre for audiences of age 18?
SQL: SELECT T1.genre FROM movies2directors AS T1 INNER JOIN u2base AS T2 ON T1.movieid = T2.movieid INNER JOIN users AS T3 ON T2.userid = T3.userid WHERE T3.age = 18 GROUP BY T1.genre ORDER BY COUNT(T1.movieid) DESC LIMIT 1