Ответ:

1. It (was) very cold yesterday.

2. When (did) you (meet) him?

3. I (have not seen) him since 2006.

4. Have you gathered many mushrooms?

5. Where (have)you (put) the newspaper? I want to read it, but cannot find  it anywhere.

6. The new school (began) working last year.

7. At last, I (have done) all my homework: now  I shall go out.

8. The building of the house (began) early in April.

9. The rain (has stopped) but a cold  wind is still blowing.

10. We (have) already (solved) the problem.

11. Не (came) a moment ago.

12. I've never (spoken) to him.

13. Не (has) just (finished) his work.

14. Have you (made) any spelling mistakes in your  dictation?

15. What books (did) you (read) when you (lived) in the country? 16. They (have not yet come) from  the south.

17. Не (was) ill last week, but now he (has recovered).

18. If everybody (has read) this new novel,  let's discuss it.

19. Have you (booked) tickets?  Yes,  I (booked) them several     days ago.

20. - I can  hardly recognize you. I (haven't seen) you since you

(left) for Moscow.    - And you (have changed) so much.

Объяснение: