单项选择题

A.高差不足0.30m两级踏步时,其坡度不宜应大于1:10
B.高差不足0.30m两级踏步时,其坡度不应宜大于1:8
C.高差不足0.40m三级踏步时,其坡度不应宜大于1:10
D.高差不足0.40m三级踏步时,其坡度不应宜大于1:8