Change the following sentences to passive voice

Change the following sentences to passive voice
11. Her sister is preparing the breakfast in the kitchen.
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12. We should clean our teeth at least once a day.
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13. The shop assistant handed the packages to the customer.
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14. The director award the first prize to the best competitor.
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15. The organizer says that the performance will start at 7 p.m.
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16. He recommended that we shouldn't stay in the suburb.
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17. I had a technician repair my mobile phone.
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18. They often get the technician to maintain the water heater.
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19. How long have you waited for the dentist?
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20. People saw her plant the tree.
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