________ something wrong with the machine, I am afraid.

A．There seems to have

B．There seems to be

C．He seems to be

D．It seems to be

导致离心泵汽蚀现象发生原因中，描述不正确的是（）。

A.入口管线阻力大

B.泵输出流量过小

C.泵输出流量过大

D.泵入口压力下降