Hoa began playing piano when she was ten
→ Hoa has been playing piano since she was ten.
7. Mr Hai began to be a doctor when he was 21
→ Mr Hai has been being a doctor since he was 21
8. Hung stopped playing soccer last year
→ Hung hasn’t been playing soccer since last year
9. I stopped smoking 2 years ago
→ I haven’t been smoking for 2 years 
10. She stopped writing when she moved to England
→ She hasn’t been writing since she moved to England
11. My brother stopped working in this factory last month
→ My brother hasn’t been working in this factory since last month.
12. Maria stopped planting flowers 10 years ago
→ Maria hasn’t been planting flowers for 10 years
13. Ba started building this hotel a year ago.
→ Ba has been building this hotel for a year
14. She stopped playing volleyball a year ago
→ She hasn’t been playing volleyball for a year
15. We began listening to music at 4pm
→ We have been listening to music since 4PM
16. I left there last month
→ I haven’t been there since last month
17. When did you live here?
→ How long have you lived here?
18. When did you know her?
→ How long have you known her?
19. How long have you written this book?
→ When did you start writing this novel?
20. Ba has worked in this factory since he was 18
→ Ba started working in this factory when he was 18 years old