Why do textbooks divide information into units, chapters, lessons, and sections

Read this passage: byron and mitch are co-captains of the mathletes, their high school's academic team. they are backstage with the five other team members, preparing to compete in the state math quiz. byron sits on the floor with his eyes closed and his earbuds in, listening to classical jazz, which him focus his mind and energy. suddenly, he feels a presence beside him. he opens his eyes to see mitch staring at him. "mathletes! mathletes! " mitch chants loudly. mitch gives byron a thumbs-up and then proceeds to strut around like a peacock, high-fiving the other team members, as byron shuts his eyes again and does his best to refocus his mind which statement best summarizes the passage?