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1. They have been studying for three hours already.

2. Mike has been learning English for three months.

3. I've already washed the dishes.

4. Have you ever been to Singapore?

5. I haven't seen Jim for a week.

6. I've been thinking about your proposal the whole day.

7. I've done three exercises today.

8. It has been raining since morning.

9. I've waited for you for an hour.

10. She's been making a cake for three hours and she hasn't finished yet.

11. He's been very busy recently.

12. I've never been to Jamaica.

13. He's broken his finger.

14. I've written ten letters to you, and you haven't written back yet.

15. How long have you been running?