单项选择题

某厂房设计降雨强度q=478L/(s·h㎡),屋面径流系数w=0.9,拟用屋面结构形成的矩形凹槽做排水天沟,其宽B=0.6m,高H=0.3m,设计水深h取0.15m,天沟水流速度V=0.6m/s,则天沟的最大允许汇水面积应为以下何项?( )

A.125.52㎡
B.251.05㎡
C.1255.23㎡
D.2510.46㎡