Since или for. Урок английского языка

1. I haven't slept sincefor 48 hours.

2. My boss has been away sincefor half a day only.

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

4. They haven't visited us sincefor Christmas.

5. You have been watching TV sincefor hours.

6. He hasn't played the piano sincefor he was a boy.

7. These cherry trees have bloomed every spring sincefor 1980.

8. They have been raising horses and cows on their farm sincefor many years.

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

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