1. Nina has been learning/has learned English for 2 years.
2. The birds have already flown/have been flying to the South.
3. They have known /have been knowing him for many years.
4. Mike has forgotten/has been forgetting to learn the poem.
5. The children have been watching/have watched cartoons for 2 hours.
6. The train has just come/has been coming.
7. We haven’t been having/ haven’t had a holiday for 5 years.
8. She has been teaching/has taught at this school for twenty years.
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.