1. It has started raining an hour ago⇒ bỏ has
2. I knew Hoa for some months.⇒ has known
3. We didn’t see Nga since Monday.⇒ haven't seen
4. Lan was in the USA for 2 years.⇒ has been
5. I have gone to bed at 10 o’ clock last night⇒ went
6.They moved to London for 2003.⇒ in
7. How long have you learn English ?⇒ learned
8. Peter was ill for a week.⇒ has been