Read the passage carefully and choose the correct answer.

Tet, or Vietnamese New Year, is the most important celebration in Vietnamese culture. Tet celebrates the arrival of spring based on the Chinese calendar, which usually has the date falling in January or February. Tet is generally celebrated on the same day as Chinese New Year. It takes place from the first day of the first month of the Vietnamese calendar (around late January or early February) until at least the third day. Many Vietnamese prepare for Tet by cooking special holiday food and cleaning the house. These foods include chung cake, day cake, dried young bamboo soup, and sticky rice. Many customs are practiced during Tet, such as visiting a person’s house on the first day of the new year, ancestor worship, wishing New Year’s greetings, giving lucky  money to children and elderly people, and opening a shop. Tet is also an occasion for pilgrims and family reunions. They start forgetting about the troubles of the past year and hope for a better upcoming year.    

What is the most important Vietnamese celebration?