1.It's impolite of them to wear hats in the pagoda(shouldn't)
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2.Children have to live with their parents until they reach the age of 18(obliged)
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3.Is it necessary for me to tip in a coffee shop?(have to)
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4.It's not mandatory for staff to wear vests in their company(need)
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5.It's good for us to keep our traditional customs(should)
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