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PART 4.

 4 -> 2 -> 7 -> 6 -> 1 -> 5 -> 3

PART 5.

1. Tomorrow, I will vitsit my grandparents in the countryside.

2. We won't burn fireworks at the New Year celebration.

3. They will buy Banh Chung at Tet, they will cook them before Tet.

4. He won't go to school at Tet, he will go out with friends.

5. She will buy new clothes for her family at Tet.

6. We will behave well with each other from now.

7. We won't fight to make our teacher unhappy.

8. We won't give presents to our friends at Tet.

9. We will dress beautifully and go out with friends.

10. She will buy peach blossoms to decorate her house at Tet.