Choose the right tense form.
1. We haven’t been having/ haven’t had a holiday for 5 years.
2. She has been teaching/has taught at this school for twenty years.
3. David has been painting/has painted in his studio since 10 o’clock.
4. Mary and Sam have collected/ have been collecting stamps for 3 years.
5. Their parents have been/have being friends since their childhood.
6. Dave has been/ has been being a student for 2 years.