單項選擇題一般排水溝的橫斷面和縱向坡度不宜小于()。

A.0.4m×0.4m,0.1%
B.0.5m×0.5m,0.1%
C.0.4m×0.4m,0.2%
D.0.5m×0.5m,0.2%