| Increasingly, historians are blaming
diseases imported from the Old World for the great disparity between the native
population of America in 1492--new estimates of which jump as high as 100
million, or approximately one-sixth of the human race at that time--and the few
million full-blooded Native Americans alive at the end of the nineteenth
century. There is no doubt that chronic disease was an important factor in the
sharp decline, and it is highly probable that the greatest killer was epidemic
disease, especially as manifested in virgin-soil epidemics. Virgin-soil epidemics are those in which the populations at risk have had no previous contact with the diseases that strike them and are therefore immunologically almost defenseless. That virgin-soil epidemics were important in American history is strongly indicated by evidence that A. could scarcely ward off the fatal attack by the 1952 epidemic. B. were immunologically defenseless against measles. C. were the last native people to be struck by a virgin-soil epidemic. D. did not come into frequent contact with White Americans until the 20th century. [单选题][单选]下列关于类风湿关节炎诊断依据，不包括（ ）。
A.对称性腕关节、掌指关节、近端指间关节疼痛肿胀>6周 B.X线改变 C.RF阳性 D.类风湿结节 E.抗核抗体阳性 [单选题]预应力混凝土桥跨结构的混凝土强度等级不应低于()。《修规》第3.5.3条
A.70 B.50 C.60 D.40 [单项选择]组织工具是组织论基本理论应用的手段，基本的组织工具除项目结构图外，还有组织结构图、任务分工表、管理职能分工表和( )等。
A. 网状结构图 B. 企业策划方案 C. 工作流程图 D. 以上都不是 [单选题] 在峰前到达场，每条到发线靠近驼峰调车场的一端，应装设( )信号机。
A.驼峰辅助 B.驼峰复示 C.进路 D.出站 [简答题]“六个到位”具体内容是什么？
[填空题]25Hz电源模块相位是局部超前轨道 。
[填空题]在矩阵组织中发展项目班子的最有效方法是遵照（）
[单选题]No failure in braking system and green hydraulic pressure is available, other requirements of Automatic Braking System ARM are
A. the anti-skid system has electric power B. at least one ADIRS is functioning C. all of above [判断题]天然气不充分燃烧,易产生一氧化碳。( )
A.正确 B.错误 我来回答: 提交
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