Rút gọn biểu thức

11. The students will be awarded the present. The students' reports are very valuable.
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12. The book was a lovely story. I was reading it yesterday.
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13. The botanist will never forget the day. He found a strange plant on that day.
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14. Someone is phoning you. He looked for you three hours ago.
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15. The man works for my father's company. The man's daughter is found of dancing.
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16. The girl was injured in the accident. She is in hospital now.
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17. Can you pick up the paper? They are lying on the floor.
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18. I don't like the man. He is going out with my sister.
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19. Yesterday I met a man. He works with your brother.
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20. I know a shop. It sells really good meat.

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giúp mình bài 9 vs ạ!!!

Để đốt cháy hoàn toàn 3,9g hỗn hợp bột Mg và bột Al cần dùng vừa đủ 2,24 lít khí O2( ở dktc).Tính thành phần trăm của 2 kim loại trong hỗn hợp trên