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如何区别和理解民族同化、民族分化、民族组合、民族融合、民族消亡？
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Commuting to work in Chicago is no【C1】______, for the roads there are even more crowded than in San Francisco. But here is how the city of Chicago is handling the problem. "We dont have rash hours any more," said Charles M. Mclean, who runs the nations busiest road. "We have rash periods, and they keep【C2】______longer and longer. " In Chicago, a【C3】______system has been developed that controls【C4】______the citys seven expressways. Now, one mana controller can【C5】______the movement of Chicagos traffic【C6】______looking at a set of lights. The system uses electronic sensors that are built into each expressway, half a mile【C7】______. Several times a second, the computer【C8】______information from each sensor and translates it into green, yellow or red lights on a map in the control room. "See that red light near Austin Avenue?" the controller asked a visitor, "Thats a repair truck【C9】______the road, and the traffic has to go【C10】______it. " At the Roosevelt Road entrance【C11】______the expressway, the light kept【C12】______from green to red and back to green again. "A lot of trucks get on the expressway there. " the controller explained. "They cant speed up as【C13】______as cars. " The sensors show【C14】______where an accident or a stopped car is blocking traffic,【C15】______a truck is sent by radio to clear the road. The system has lowered the【C16】______of accidents by 18 percent. There are now 1. 4 deaths on Chicagos expressways for each one hundred million miles traveled,【C17】______in other parts of the country there are 2. 6. Traffic experts say that the Chicago system is the "coming thing". Systems like Chicagos are already in use on some expressways in Los Angeles and Houston. "Chicago has【C18】______the lead," says New York Citys【C19】______director; and he adds, "we are【C20】______".【C1】A．cheerfulB．pleasantC．happyD．pleasure
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诊断子宫性闭经最简便而可靠的方法是（）
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圆筒炉的炉管排列形式有（）两种
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按简化的弹性力学模型计算的应力值不能用于()。
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下列属于屏蔽泵易损坏件的是（）
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《燕山夜话》、《三家村礼记》、《长短录》等专栏的作品有何特点和意义？《燕山夜话》等作品的特点和意义是什么？
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关于肋间肌的描述，哪几项是正确的？（）
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长期卧床者呼吸系统的变化错误的是（）。