Chuyển những câu bị động dưới đây thành câu chủ động

Bài 4: Chuyển những câu bị động dưới đây thành câu chủ động.                                                                       
4. How long has this fax machine been used by Mr. Green?
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5. The singer was not recognized by his fan when he was at the restaurant.
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6. He will be disqualified from the competition by the judges if he uses drugs.
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7. All the unnecessary lights will be turned off to save energy.
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8. Jane was prevented from staying up too late by her mother.
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9. Was this document typed by Mr. Brown?
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10. Many dead people were found by the recues after the earthquake.
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