What's Mark Twain's attitude toward the examination in Chapter 21 of The Adventures of Tom Sawyer? A: The examination only allows mechanic imitation but lacks of innovation. B: The long sermons students add to the end of their compositions are boring and didactic C: The topics students choose to make compositions are new and creative D: The audience present at the examination shows sincere applause to the students' performance especially when they add long sermons to their compositions