单项选择题
A.急流向急流过渡的水力现象 B.急流向缓流过渡的水力现象 C.缓流向急流过渡的水力现象 D.缓流向缓流过渡的水力现象
A.0.1 B.0.2 C.0.4 D.0.5
A.0.20m B.0.30m C.0.40m D.0.50m