What is the average height of the superheroes from Marvel Comics?
superheroes from Marvel Comics refers to publisher_name = 'Marvel Comics'; average height of the superheroes refers to AVG(height_cm)
SELECT AVG(T1.height_cm) FROM superhero AS T1 INNER JOIN publisher AS T2 ON T1.publisher_id = T2.id WHERE T2.publisher_name = 'Marvel Comics'