单项选择题

A.桥面纵坡大于 2%、桥长小于 50m 时,按 12~15m 间隔设置
B.桥面纵坡小于 2%、桥长小于 50m 时,不需设置
C.桥面纵坡大于 2%、桥长大于 50m 时,可不设置
D.桥面纵坡小于 2%,按 6~8m 间隔设置