What is the problem with Russias space station？
A. It has lost its primary 6xygen sources.
B. It has lost its backup oxygen sources.
C. It has lost both the primary and the backup oxygen sources.
D. It has last neither the primary or the backup oxygen sources.
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The main idea of the passage is that the United States Presidents should ______
A. have wide political experience
B. serve for a term of less than six years
C. serve for a term of more than six years
D. be allowed to be reelected
苯并二氮杂革类药物盐中被置换出的无机酸类，在醋酸介质中的酸性强弱顺序
A. 高氯酸＞氢溴酸＞硫酸＞盐酸＞硝酸
B. 高氯酸＞硫酸＞盐酸＞氢溴酸＞硝酸
C. 硫酸＞盐酸＞氢溴酸＞高氯酸＞硝酸
D. 硫酸＞高氯酸＞氢溴酸＞盐酸＞硝酸
E. 氢溴酸＞硝酸＞硫酸＞盐酸＞高氯酸
奎宁是一种弱碱，溶剂滴定应选择的溶剂为
A. 纯水
B. 液氨
C. 冰醋酸
D. 甲苯
E. 甲醇
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