- Without transportation, there could be no trade. Without trade, there could be no towns and cities. Towns and cities are traditionally the ___16___ of civilization. Therefore, transportation helps make civilization ___17___ . Throughout most of the prehistoric period, people lived by hunting, fishing, and ___18___ wild plants. They had no beasts of burden, wheeled vehicles, or roads. People traveled ___19___ and carried their infants and belongings strapped to their backs or heads. Loads too heavy for one person to carry were strapped to a pole and carried by two people. ___20___ , people learned that they could drag loads along the ground on sledges. During late prehistoric times, people began to build sledges with runners. When people developed agriculture and began to establish ___21___ settlements, trade between settlements started to develop, which created a need for better ___22___ of transportation. The donkey and the ox, which had been tamed for food products and farm work, helped ___23___ this need. The use of donkeys and oxen as beasts of burden enabled people to ___24___ heavier loads than they could before. People also began to develop water transportation during prehistoric times. They built rafts of such __25____ as logs or reeds. Later, people learned ___26___ to make dugouts and canoes. People paddled these early craft with their hands or propelled them with paddles or __27____.The wheel was invented about 3500 B.C. and sailboat about 3200 B.C. Wheeled vehicles and sailing vessels ___28___transportation. But the speed of transportation improved only ___29___ over the centuries. Inventors produced the first engine- ___30___ vehicles during the late 1700’ s and the early 1800’ s. This development marked the beginning of a revolution in transportation that has continued to the present. 16. A. highlights B. pinpoints C. headquarters D. centers17. A. possible B. acceptable C. practical D. typical18. A. growing B. gathering C. watering D. moving19. A. in turn B. at ease C. on foot D. for fun20. A. All the while B. For a while C. In time D. On time21. A. temporary B. permanent C. regular D. steady22 A. knowledge B. judgment C. standards D. means23. A. recognize B. develop C. meet D. reduce24. A. bear B. move C. share D. lift25. A. materials B. styles C. items D. types26. A. where B. when C. how D. as27. A. poles B. sails C. currents D. winds28. A. demonstrated B. revolutionized C. witnessed D. initiated29. A. considerably B. continuously C. swiftly D. slightly30. A. powered B. controlled C. oriented D. related
- 名词解释：卫生法
- 暴露因素与疾病的关联形式有______、虚假关联、伴随关联和因果关联。
- 统计表多采用三线条，即顶线、______ 、纵标目下的横线。
- 戒断反应是毒品作用于人体，使人体产生适应性改变，形成在药物作用下的新平衡状态，一旦停掉药物，______就会发生紊乱，出现一系列严重反应。
- 情绪是人类特有的一种心理现象，表现在主观感受和______上。
- 为了创建卫生、安全、满意和高效的劳动环境，促进经济可持续发展，世界卫生组织和国际劳工组织对职业卫生与安全工作提出了______项原则。
- 食品添加剂按生产方法分为化学合成、生物合成和______三大类。
- 蛋白质是人体的重要组成成分，约占正常人体重的______%
- 根据污染物的毒性可将化学性污染分为一般化学物和______两类。
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