9. David has been painting/has painted in his studio since 10 o’clock. 10. Mary and Sam have collected/ have been collecting stamps for 3 years.
11. Their parents have been/have being friends since their childhood.
12. Dave has been/ has been being a student for 2 years.
Present Perfect
9. David has been painting in his studio since 10 o’clock.
10. Mary and Sam have been collecting stamps for 3 years.
11. Their parents have been friends since their childhood.
12.Dave has been a student for 2 years.