Make questions for the underlined parts:
1. They decorate their house with beautiful Christmas trees → hien tai
What did they decorate their house with?
2. I don't like ice swimming because it's dangerous. → hien tai
Why do't you like ice swimming?
4. Last year I went to Thailand with my parents -> qua khu
Who did you go to Thailand with last year
5. This festival is held in my country every two years. → hien tai
How often is this festival held in your country
6. I prefer Thai food to Japanese food. → hien tai

Which food do you prefer: Thailand food or Japanese food [ câu này không dùng what đc ạ ]
7. Those are my grandfather’s pictures, → hien tai
Who are those picture belong to? [ nếu dùng WHOSE đứng đầu thì không thể dùng those theo câu hỏi đc ]
8. They celebrate the festival after harvesting the crop. → hien tai don
When do you celebrate the? 

CHÚC BẠN HỌC TỐT ^^