1. at the health center là địa điểm, dùng Where
Where did your friends volenteer last saturday?
2. raised money là hành động làm gì dùng What
what did your uncle do to help children with cancer?
3. hỏi lý do tại sao dùng why
why did the students plant trees along the streests?
4. what did you recycle to help the environment?
5. three số đếm được dùng How many 
How many beach clean - ups did they organize last year?
Cấu trúc câu hỏi (WH) quá khứ đơn : (WH) + did + S + V_ inf....?