Question

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

Answer 1

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.

Answer 2

Let's correct the sentences using the present perfect tense:

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.

In these sentences, the present perfect tense is used to indicate actions or states that started in the past and have relevance to the present.