单项选择题
A.30%,60%B.30%,50%C.40%,60%D.40%,80%
A.60°和90°,内摩擦角B.60°至90°,内摩擦角C.60°和90°,休止角D.60°至90°,休止角
A.2%,60%~82%B.10%,30%~60%C.5%,30%~60%D.5%,60%~82%