单项选择题
A.一层 B.二层 C.三层 D.四层
A.80mm,6mm B.60mm,6mm C.80mm,8mm D.60mm,8mm
A.底层 B.顶层 C.中间层 D.不作要求
A.3mm,2mm B.4mm,2mm C.4mm,3mm D.3mm,1mm
微信扫一扫,加关注免费搜题