练习说明
段落填空 题目要求： 阅读文段，从文中挑选原词补全句子，每道题目都有特定的字数要求，以黑体加粗字标示。请把答案填到每题空缺处。
Questions 8-13
Complete the notes below.
Choose ONE WORD ONLY from the passage for each answer.
Write your answers in boxes 8-13 on your answer sheet.
原文
Once chickens were domesticated, cultural contacts, trade, migration and territorial conquest resulted in their introduction to different regions around the world over several thousand years. Chickens arrived in Egypt in around 1750 BC, as fighting birds and additions to zoos. Drawings of the birds decorated royal tombs, which contained the treasures that the kings and queens would take to the afterlife. Yet it would be another 100 years before the bird became popular among ordinary Egyptians.
It was in that era that Egyptians mastered the technique of artificial incubation, which freed hens to lay more eggs. This was not easy. Most chicken eggs will hatch in three weeks, but only if the temperature remains at around 38 degrees Celsius. The eggs must also be turned three to five times a day, and the humidity must remain stable at about 55 percent, otherwise physical deformities can result, or the eggs won't hatch. The Egyptians constructed vast complexes of large rooms, which were essentially ovens, and these were connected to a series of corridors and vents that allowed attendants to regulate the heat from fires. The egg attendants kept their methods a secret from outsiders for centuries.
Around the Mediterranean, archaeologists have uncovered chicken bones from about 800 BC. Chickens were a delicacy among the Romans, whose culinary innovations included the omelette, and the practice of stuffing birds for cooking. European farmers began developing methods to fatten the birds, such as feeding them bread which had been soaked in wine. But the chicken's status in Europe appears to have diminished with the collapse of Rome. In the period after the fall of the Roman Empire, chicken farms vanished and the birds returned to the size they had been 1 000 years earlier.
Well into the 20th century chickens, although valued as a source of eggs, played a relatively minor role in diet and the economy. Long after cattle had entered the industrial age of centralized and mechanized large-scale production, chicken production was still mostly a small-scale, local enterprise. The breakthrough that made today's huge bird farms possible as the inclusion of antibiotics, along with a mixture of different vitamins, in the food chickens ate. This allowed chickens to be raised indoors and be protected from cold temperatures and heavy rain as well as predators. This factory farming represents the chicken's final step in its transformation into a big protein-producing business.