Нужно исправить ошибки в предложениях
1. What are you doing when the police arrived?
2. Mary can't answer the questions. She hadn't read the text yet.
3. It is often snow in December.
4. The lesson started since twenty minutes ago.
5. These pupils have finished Unit Fifteen last week.
6. They have been written the test for an hour.
7. John is doing exercises since 8 o'clock

1. What were you doing when the police arrived?2. Mary couldn't answer the questions. She hadn't read the text yet.3. It often snows in December.4. The lesson started twenty minutes ago.5. These pupils finished Unit Fifteen last week. 6. They have been writing the test for an hour.7. John has been doing exercises since 8 o'clock

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