Since или for. Урок английского языка

1. You haven't smoked sincefor two months.

2. We've been friends with Fred sincefor decades.

3. I haven't slept sincefor 48 hours.

4. We've lived here sincefor seventeen years.

5. We haven't seen Mary sincefor the party.

6. I've read two books sincefor the weekend.

7. They have been ill sincefor Monday.

8. He worked at that company sincefor ten years before he retired.

9. New ideas have been put into practice sincefor he was elected our leader.

10. They've been teaching here sincefor quite a long time.