After long and hard work，the police at last discovered the________of the baby found by the side of a

road.[ ]

A．dialect  

B．identity

C．situation  

D．condition

等距离抽样或机械抽样方法又称为（）

A.单纯抽样

B.系统抽样

C.分层抽样

D.整群抽样

E.多级抽样