This document discusses how Americans use modals to express differing opinions and uncertainty in a respectful manner. It provides two dialogues as examples. In the first, Sue uses modals like "I would" and "if I were you" to politely suggest to Sarah that baking a blackberry cream cheese pie may not be the best choice for her new Chinese roommate, as different cultures have different tastes. In the second dialogue, Sue tells her mother about Sarah's pie idea, and her mother responds with disbelief using the expression "You're not serious?" The document concludes with stating that modals can also express encouragement and lists some additional expressions for conveying disbelief.