单项选择题
A.0.1~0.25N/mm2 B.0.25~0.5kN/mm2 C.0.1~0.25kN/mm2 D.0.25~0.5N/mm2
A.预应力砼 B.钢筋砼 C.防水砼
A.10 B.15 C.20