The author uses alliteration to create a playful mood
Yes, because her class represents a random sample of students in the school. Instead of asking every single student in the school, which would take too long, it is much easier to poll a small group of people to see what they think, and then have their opinion represent a larger community. Although if Maggie had asked more people, her answer would have been more precise, the sample could still be highly accurate. Hope this helps even though I am asking the day after this was posted and this question is in the wrong subject. It should be in math, but it's not that big of a deal.
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The notion that united americans' different backgrounds and cultures in a single one is <em>patriotism</em>. She defines it as "taking pride in this unlikely ability to throw all of us together in a country that across its length and breadth is as different as a dozen countries, and still be able to call it by one name." It's what keeps America a single country, despite the different origins and backgrounds of its inhabitants.