Here are the best options to complete the passage:

1. **D. day**
2. **A. festival**
3. **B. light**
4. **A. red**

So the completed passage would read:

Vu Lan Festival takes part on 15th of the seven lunar **day**. It is one of the largest festivals of Viet Nam. Vietnamese people consider that it is an occasion for family gatherings as well as expressing love and gratitude to ancestors and parents. Vu Lan (2) is known as Mother’s Day in Viet Nam. First, in the morning of that day, a lavish tray with various delicious dishes is set on the altar, and the householder will (3) **light** incense and invite ancestor to come back home and celebrate with family. Then, at night the Vietnamese hold a ceremony of releasing lighted lanterns on the river, they believe by doing that their wishes for parents will come true. They also go to the pagoda, wearing either a **red** rose if their mothers are alive or...