题干
Until the start of the Industrial Revolution, mankind was poor, hungry, and constantly at the _______ of disease and natural disasters．
A：power
B：limit
C：control
D：mercy
答案(点此获取答案解析）
D
枚最新研制的某型导弹中随机抽取
枚来进行发射试验，用每部分选取的号码间隔一样的系统抽样方法确定所选取的