Rewrite the sentences

6. My students learnt a lot of interesting experience from this man last week.
My students have....
7. She has never seen a dirtier-looking dog before.
→ This is the first time
8. When did your brother move to Iraq?
→ How long has
→ How long is it
9. I haven't seen my son for ages.
→ It is........
→ The last time.....
10. Tom hasn't been to HN before.
→ This is
11. My sister started to work for an enterprise when she graduated from university.
→ My sister........
12. I have lived in Hoi An since June 4th, 2001.
→ I moved
13. The last time I went to HN was in May.
→ I haven't ......
14. I have not been there for a long time.
→ The last time.....
15. He hasn't visited me since May.
→ The last time.......
16. No one has challenged his authority before.
→ This is the first time his.
17. Since I was in this city, I have not seen him.
→ I last .......
18. It became more and more difficult to get into university in 1999.
→ It has been
19. The car industry in England has developed for many years now.
→ It has .....
20. How long is it since Kate last replied your email?
When......