True, the narrator can be all of those things. Some examples include the following:
Major Character who's the narrator: Hazel Grace Lancaster in The Fault in Our Stars
Minor Character who's the narrator: Nick Carraway in The Great Gatsby
Protagonist: Esther in Sylvia Plath's The Bell Jar (narrated in 1st Person POV)
Antagonist: Amy Dunne in Gone Girl by Gillian Flynn
Answer:
Arnold should use simple language that highlights the entertainment value of the game.
Explanation:
Arnold should try to make his pitch as simple and as interesting as possible. This would make them listen Arnold carefully and learn even more difficult concepts.
Formal academic language will make the children feel bore and their interest will be lost.
Children will not be able to understand Technical language and as result will get impatient and lose their interest and attention.
Children are not much concerned about how popular they game will become. Children will listen to Arnold as long as he entertains them.
Always treat others in a good manner no matter what their social status is.... at least that's what I learned from it ;)