Only by shouting at the top of his voice _____.[ ]

A. he was able to make himself hear

B. he was able to make himself heard

C. was he able to make himself hear

D. was he able to make himself heard

关于流动流体的物料衡算，下列说法正确的是（）。

A、对于定态流动系统，单位时间进入各截面的流体质量相等

B、可压缩流体流经各截面的体积流量相等

C、对于定态流动系统，单位时间进入各截面的流体体积相等

D、定态流动系统中，流体在管路中的流动规律与管路上的管件、阀门及输送设备有关