1. Поставьте глаголы в скобках вверную форму : 11. Helen. (to wash) the dishes for fifteen minutes.
12. My classmates (to write) a dictation since the beginning of the lesson.
13. Sam (to drive) a car for five hours now.
14. I... (to look) for information on the subject since last Friday.
15. Molly ... (to paint) this picture for three days now
16. The tourists ... (to do) the sightseeing since nine o'clock.
17. You ... (to work) as a computer programmer for more than fifteen years.
18. The wind ... (to blow) since yesterday .
19. My grandfather ... (to collect) coins since he was a boy.
20. Andy and Den
(to discuss) the plans for their winter holidays for two hours now.​

1. Helen has been washing the dishes for fifteen minutes.
Explanation: We use the present perfect continuous tense (have/has + been + verb-ing) to talk about actions that started in the past and are still happening at the present moment. In this case, Helen started washing the dishes in the past and is still doing it at the moment.

2. My classmates have been writing a dictation since the beginning of the lesson.
Explanation: Similar to the previous sentence, we use the present perfect continuous tense to indicate that an action started in the past and is still ongoing. In this case, the classmates started writing the dictation at the beginning of the lesson and are still doing it.

3. Sam has been driving a car for five hours now.
Explanation: Again, the present perfect continuous tense is used to describe an action that started in the past and is still happening. Sam started driving the car five hours ago and is still driving it at the moment.

4. I have been looking for information on the subject since last Friday.
Explanation: Once again, the present perfect continuous tense is used to indicate an action that started in the past (last Friday) and is still in progress. The person has been searching for information since that day and is still doing so.

5. Molly has been painting this picture for three days now.
Explanation: The present perfect continuous tense is used to describe an action that started in the past and continues in the present. In this case, Molly started painting the picture three days ago and is still working on it.

6. The tourists have been doing the sightseeing since nine o'clock.
Explanation: The present perfect continuous tense is used to show that an action started in the past and is still happening. In this sentence, the tourists began their sightseeing at nine o'clock and are still engaged in it.

7. You have been working as a computer programmer for more than fifteen years.
Explanation: Here, the present perfect continuous tense is used to express the duration of an action that started in the past and continues until now. The person has been working as a computer programmer for more than fifteen years, indicating that they started in the past and are still doing it.

8. The wind has been blowing since yesterday.
Explanation: The present perfect continuous tense is used to describe an action that started in the past (yesterday) and is still ongoing. In this case, the wind started blowing yesterday and is still blowing now.

9. My grandfather has been collecting coins since he was a boy.
Explanation: The present perfect continuous tense is used here to show that an action started in the past (when my grandfather was a boy) and continues in the present. In this sentence, my grandfather started collecting coins when he was young and still does it now.

10. Andy and Den have been discussing the plans for their winter holidays for two hours now.
Explanation: The present perfect continuous tense is used to indicate an action that started in the past and is continuing in the present. In this case, Andy and Den began discussing the plans for their winter holidays two hours ago and are still discussing them.