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城镇土地使用税只对国内企业、单位；和个人开征，对外商投资企业、外国企业和外籍个人不征收。()
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Every year landslides (滑坡) cause 25 to 50 deaths and ＄1.5 billion in damage in the U. S. They account for 15 percent of the deaths from natural disasters in Europe. And in December, a single event killed more than 200 people in the Philippines. Sending workers to stabilize (加固) mountainsides using steel bars and cement (水泥) can help prevent disaster, but it introduces new difficulties. Shaking drills produce harmful dust and loosen heavy, dangerous debris (岩屑).
"It's quite a risky job," says Giorgio Pezzuto of D'Appolonia, an engineering company in Italy.
D'Appolonia, working with eight other companies, may have an answer: a three-ton robot called Roboclimber. "The idea is to operate a machine far away that can drill without a human being on board," says Pezzuto, manager for the project, which is supported by the European Commission. Engineers claim that the machine will be faster and cheaper than manual labor. The robot, a large radio-controlled four-legged mechanical spider, has cost at least ＄2 million so far. The final product should be able to climb unstable mountainsides, drill holes, insert bars and cement, and collect data on the slope's stability. Testing should begin in May.
The underlined word "event" in the first paragraph refers to______.
研究城市生态系统包括()。
①研究城市生态系统的主体———城市人口与城市环境的相互关系;
②研究城市生态学要素或环境要素的特点;
③衡量城市人类生存环境质量的生态学指标;
④研究城市物质代谢与能量流动过程与城市环境质量的相互关系;
⑤研究城市除人以外的生命有机体的状况,及其与人类的相互关系;
⑥从全球角度研究城市化对整个地球生命支持系统的影响;
⑦从区域角度研究城市生态系统与其他生态系统的相互关系
一患儿突发右小腿痛，活动障碍，X线示右胫骨中段骨折，骨折端膨大，骨皮质变薄。引起骨折的主要因素是（）E．
保税货物包括加工装配类和储存类保税货物。 ()
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