离心泵的水力损失是理论扬程与实际扬程的差值。
参考答案：对
It was reporfted that eight policemen weresent to the forest ____ the missing girl. [ ]
A. in need of
B. in search of
C. in charge of
D. in time of
在运行路线的最大坡道上用（）挡起步
A.1
B.2
C.3
D.4
