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2 năm trước
cho p là số nguyên tố và p^2+2 cũng là số nguyên tố . chứng minh p^3+2 cũng là số nguyên tố
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Tigers are one of the most powerful and graceful animals in the world. The different species that still exist today, namely the Bengal, Indochina, Siberian, South China and Sumatra tigers are in danger of becoming extinct. Due to irresponsible hunting, the Bali, Caspian and Java tigers have already become extinct. This could soon happen to the other species too. In the past, tigers were considered as pests. With a smaller area to hunt, as man had taken up more of the land to build upon, the tigers found less area for themselves to hunt. They thus turned to farms to get their food. Farmers’ livestock were attacked by these tigers. People were then encouraged to hunt and kill these animals with the promise of rewards. Even after the threat of tigers on livestock was over, man continued to hunt tigers, this time for recreation. Poachers too hunt tigers for their body parts knowing that the skin of tigers is much sought after. Bones and other organs are also used as ingredients in traditional Chinese medicine. Although killing is illegal, it is still being carried out unless it is stopped, the remaining species of tigers will soon become extinct too. 24. How many species of tigers were there originally? A. three B. Four C. Five D. eight 25. There were fewer hunting grounds for the tigers because _____ A. man had occupied the land B. the farmers put their livestock there C. the tiger population was becoming bigger D. they liked hunting livestock 26. Man continues hunting tigers even they are no longer pests because _____ A. he treats it as a form of recreation B. he loves tigers very much C. he still thinks tigers are pests D. he wants to make the tigers extinct 27. Poachers are people who _____ A. look after tigers B. make Chinese medicine C. hunt tigers illegally D. hunt tigers’ body parts 28. Illegal poaching will _____ A. cause the extinction of tigers C. increase the amount of Chinese medicine B. increase the amount of Chinese medicine D. increase the price of body parts Read the following passage and mark the letter A, B, C, D to indicate the word that best fits each numbered blank. Rivers all of the world’s most important natural resources. Many cities are on large rivers, and (29) __________ every country has at least one river that plays an important part in the lives if its people. Besides transportation, rivers (30) _________ food, water for crops, water to drink and opportunities for recreation for people who live along their bank and in order to get water for crops engineer sometimes build a dam (31) __________ a river and let the water become a lake behind the dam. Then people can use their water not only to irrigate fields but also to make electricity for home and industries. However, the water often becomes pollutec when cities (32) __________ river bank grow inside and the number of industries increases. We are learning that it is necessary to keep rivers clean if we want to enjoy the ________ of the natural resources. 29. A many B. most C. plenty D. almost 30. A. provide B. support C. assist D. create 31. A. over B. across C. among D. under 32. A. in B. at C. on D. above 33. A. interests B. benefits C. tips D. receipts Mark the letter A, B, C or D to indicate the best answer to each of the following question. 34. _______ I felt he was wrong, I decided to trust him. A. If B. Although C. As soon as D. Since 35. China is _____ far the most populated country in the world. A. as B. by C. so D. to 36. Susan rarely stays up late, _____? A. is she B. isn’t she C. does she D. doesn’t she 37. Her teacher suggested she ________ harder to pass the exam. A. studies B. studying C. study D. to study 38. He’s always busy. He has ________ time to relax. A. little B. a little C. few D. much 39. How do you say this fraction 3/5 in English? A. three over fifth B. three-fifth C. three-fifths D. three-fives 40. He’s interested in _________ research. A. working B. making C. studying D. doing

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