A.实际密度 B.表观密度 C.堆积密度 D.自然密度
A.1:2.56:4.12 B.1:2.57:4.76 C.1:2.52:4.82 D.1:2.53:4.76
A.2m B.3m C.4m D.5m
A.50mm B.60mm C.70mm D.100mm
A.1/2 B.1/3 C.1/4 D.1/5