—Whose notebook is this?
—It must be .[ ]
A. Mary
B. Marys
C. Marys'
D. Mary's
答案:D
已知某省山区、丘陵、湖区婴幼儿体格发育有较大的差异,现需制订该省婴幼儿体格发育有关指标的正常范围,调查设计最好采取
A.机械抽样
B.分层抽样
C.单纯随机抽样
D.整群抽样
E.分层整群抽样