One of the most amazing marathon races in the world is the Marathon of the Sands. It takes (76) every April in the Sahara Dessert in the south of Morocco, a part of the world where temperatures can (77) fifty degrees centigrade. The standard length of the marathon is 42.5 kilometers but this one is 240 kilometers (78) and takes seven days to complete. It began in 1986 and now attracts about two hundred runners, the majority of (79) ages range from seventeen to forty-seven. About half of them come from France and the (80) from all over the world. From Britain it costs £2,500 to enter, including return air fares. The race is rapidly getting more and more popular (81) , or perhaps because of, the hard conditions that runners must endure. They have to carry food and (82) else they need for seven days in rucksack weighing no more than twelve kilograms. In addition to (83) , they are given a liter and a half of water every ten kilometers. Runners do (84) terrible physical hardships. Sometimes they lose toenails and skin peels on their feet. However, doctors are always (85) hand to deal with minor injuries and to make sure that runners do not push themselves too far. Điền từ gì và giải thích nữa ạ, không cần gấp :">