1. It's known as Tet Nguyen Dan, or Tet
2. Yes, it is
3. It begins between January twenty-first and February nineteen
4. They tidy their houses, cook special food, clean and make offerings on the family altars
5. Yes, they do
6. No, it doesn't. It lasts ten days
7. Because Vietnamese people believe that how people act during those days will influence the whole year
