Ответ:

1. the boys couldn't climb the mountain
2. have you ever visited your cousin in Scotland
3. I went to doctor yesterday
4. she has been learning English for 2 years
5. what do you think of the weather in Spain
6. what is he doing now
7. we were walking down the street when a police car passed by
8. we had talked a lot
9. we have never read any books by this author
10. he was an interesting man when he was young
11. I think I will have a drink
12. the shop is opening at 9:00 a.m. next Monday. Но тут лучше present simple использовать the shop opens at 9:00 a.m. next Monday
13. America was discovered by Columbus
14. I will go to the dentist
15. we have been discussing the topic for many hours
16. I had been working for 12 hours when I finally went home
17. are you going to France next year?
18. they had finished their homework when I came