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问题 选择题

下列有关物质性质的说法正确的是

A．乙醇可以发生的反应类型有：取代反应、消去反应、加成反应

B．乙酸和苯酚的水溶液都有酸性，都能和小苏打反应放出气体

C．将Cl2和SO2的混合气体通入到品红溶液中，颜色肯定不褪去

D．向氢氧化铁胶体中滴加稀硫酸，开始有沉淀生成，而后会溶解

答案

答案：D

题目分析：A.乙醇的结构简式是CH3CH2OH，有羟基，能发生取代反应，羟基所连碳原子的临位碳原子上有氢原子，可发生消去反应，但由于分子结构中无碳碳双键，因而不能发生加成反应。错误。B. 酸性：乙酸>碳酸>苯酚。因此乙酸能和小苏打反应放出气体，苯酚不能。错误。C． Cl2和SO2的混合时发生反应：Cl2+SO2+2H2O=2HCl+H2SO4.如果它们按照1:2混合，则恰好反应产生没有漂白性相等物质，品红溶液颜色不褪去。如果它们不是按照1:2混合，则除了反应消耗外还有过量的氯气或二氧化硫，仍有漂白性，品红溶液颜色可能会褪去。错误。D.硫酸是电解质，加入硫酸时，首先是硫酸电离产生的离子中和氢氧化铁胶体上的电荷，胶粒之间斥力减小甚至消失，就会聚集形成沉淀，然后是酸碱发生中和反应生成容易溶解于水的硫酸铁和水，因而得到澄清溶液。正确。

单项选择题

患者男，67岁，缺失，拟行可摘局部义齿修复，末端基牙采用RPI卡环

适宜做邻面板的基牙是（）

A．下颌前牙

B．上颌前牙

C．下颌后牙

D．上颌后牙

E．都可以
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填空题

Part 4


Questions 26-45


·Read the following passage and decide which answer best fits each space.
·For questions 26-45, mark one letter A, B, C or D on the Answer Sheet.
Participation (26) high school sports is not a constitutional right. (27) , it is a privilege, paid for by taxpayers, open to students who promise to (28) certain conduct requirements on and off the field. One of these promises is to (29) from using drugs. Drug use is a serious problem among high school students. Studies show that as many as 500, 000 high school students use muscle-pumping, life-destroying substances such as steroids. Many more use illegal drugs, (30) cause discipline problems and (31) the stage for lifelong (32) .
Drug testing works to (33) and identify use. That is why drug testing is required to compete in the Olympics, the National Collegiate Athletic Association and the National Football League. (34) drug testing was instituted by these organizations, use of performance- (35) drugs has been greatly reduced. We should want (36) in schools.
Indeed, many athletes (37) testing programs, and no wonder. Without testing, athletes have to choose between drug use and a competitive disadvantage (38) the field.
Those who challenge the need for drug testing may be forgetting (39) it is like be an adolescent. Peer pressure is enormous, and one of the few effective counter-weights is the fear of being caught. More importantly, once drug use is (40) , a school can (41) to the student before he or she gets addicted or arrested.
For 25 years, public schools (42) by federal judges and civil libertarians, with results everyone can see. It is time (43) decisions on how to run public schools locally (44) officials. There is nothing unconstitutional about asking those who gain the advantages of school-sponsored athletics to contribute to the safety of other players, the integrity of the game and their own well-being. The Supreme Court should leave these programs (45) .

A．delay

B．refer

C．defer

D．deter
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