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11. Oil-lamps were used years ago.

12. He will be met in the restaurant by the boss tomorrow.

13. The Fowls are fed twice a day by the old woman.

14. Are the windows often cleaned by him?

15. Trees are not grown in her garden.

11. People used oil-lamps years ago.
- Oil-lamps were used years ago.
12. The boss will meet him tomorrow in the restaurant.
- He will be met in the restaurant  by the boss tomorrow. 
13. The old woman feeds fowls twice a day.
- The fowls are fed by the old man twice  a day. 
14. Does he often clean the windows?
- Are the windows cleaned by him ?
15. She doesn't grow any trees in her garden.
- Trees  aren't grown  in her garden.