单项选择题
A.2~4mm B.3~4mm C.4~5mm D.5~7mm
A.细砂拌制的1.5:1 B.中砂拌制的1:1.5 C.细砂拌制的1:1.5 D.中砂拌制的1.5:1
A.大于25mm B.小于25mm C.大于30mm D.小于30mm