It can be inferred from the passage that by 1870 ______.
A. the steam engine had been invented
B. a national commission on agriculture had been established
C. the U.S. horse population was about 10 million
D. technology began to be more economical
茶碱在乙二胺存在下溶解度由1:120增大至1:5，乙二胺的作用是
A. 增大溶液pH值
B. 矫味
C. 助溶
D. 增溶
E. 防腐
Which of the following is not TRUE of the investigation
A. It will last at least 7 years.
B. Cooperation from the mothers is also necessary.
C. Some independent observers play a part.
D. Researchers paid site visits to see a caretaker's personality and kids' emotional reaction.
按照FIDIC合同条件，有关监理人员的规定，下列叙述不正确的是( )。
A. 监理人员分为工程师、工程师代表和助理三个层次
B. 仅工程师才有发布开工令、停工令、复工令、批准设计变更处理重大索赔事件的权力
C. 工程师代表直接对工程师负责，不直接对业主负责
D. 若工程师代表疏忽未能指出工程质量的不合格时工程师也就失去了发出要求改正指令的权力
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