Asako: I guess you have a point there. By the way, I have a question. We usually pay individually in Japan. How come one person usually pays for everybody in Korea?
Kevin: Oh, I also thought that was very strange at first. I think the oldest person always picks up the bill.
MC: Well, you can consider it just a part of Korean culture. However, it¡¯s changing these days. Many young people like to pay individually. We also take turns paying.
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What does "It' refer to in the sentence "However, it's changing these days.'? Is 'it' an impersonal pronoun referring to an ambiguous situation? Or does 'it' refer to something which is said before?