Có 100 quả táo, chia vào 50 túi sao cho mỗi túi có ít nhất 1 quả. Chứng minh rằng nếu không có túi nào nhiều hơn 50 quả thì các túi có thể chia thành 2 nhóm thỏa mãn mỗi nhóm có 50 quả.

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Ai giỏi Anh giúp mik vs ạ , hứa sẽ vote 5* ạ Choose the word that has different pronunciation. 1. A. decided B. played C. listened D. enjoyed 2. A. biogas B. solar C. hydro D. environment 3. A. energy B. electric C. mean D. renewable Choose the word that has different stress. 4.A. musician B. scientist C. energy D. biogas 5.A. renewable B. atmosphere C. motorbike D. footprint 6.A. effective B. regular C. different D. serious Choose the best answer to fill in each blank in the passage: With the development of science and technology more and more______ is used every day. Nowadays, many rural areas(vùng nông thôn) in Vietnam have been electrified(điện khí hóa), and more electricity is needed. If everyone(8)______energy, it will quickly run out. (9)_______ at school should learn how to save energy,for example,they should turn(10)_____ the electric lights when they leave their classrooms. Moreover, we may waste electricity at home if we use a lot of light bulbs(bóng đèn). By not wasting energy, we will save a lot of (11)________resources, such as coal and oil. 7.A. energy B. electricity C. water D. air 8. A. saves B. wastes C. uses D.makes 9. A. Students B. Teachers C. Workers D. Headmasters 10.A. on B. at C.off D.up 11.A. different B. many C. solar D. natural Choose the best option to complete the sentences. 12. We should put ___________ on our roof for the heating and hot water. A. solar energy B. equipment C. cracks D. solar panels 13. Remember to ____________ the lights before going to bed. A. turn B. turn off C. turn on D. stop 14. It is a good idea to use ____________ when travelling long distances. A. cars B. taxis C. private cars D. public transport 15. What should we do to ____________ electricity? A. cut B. take C. save D. waste 16. In my opinion, nuclear power is not only expensive but also ___ to our environment. A. danger B. dangerous C. risk D. disaster 17. Someone’s carbon __________ is a measurement of the amount of carbon dioxide that their activities produce. A. effect B. amount C. footprint D. energy 18. Several governments try to ____________ the use of fossil fuels. A. reduce B. increase C. waste D. save 19. We are looking for cheap, clean and ____________ sources of energy. A. effective B. efficient C. serious D. dangerous 20.__________ source of energy is the source that can’t be replaced after use. A. Renewable B. Natural C. Effective D. Non-renewable