Since или for. Урок английского языка

1. Jane hasn't been to America sincefor 1981.

2. We've been together only sincefor a few days.

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

4. They haven't visited us sincefor Christmas.

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

6. He's been working in the field sincefor early this morning.

7. John and Bob have been working on this project sincefor five months already.

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

9. They've been in love sincefor three weeks.

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