压缩机发生喘振时，管路中气体出现反复倒流现象，出现周期性气流震荡。（）
参考答案：对
He turns deaf ear to his parents, many times they have pointed out his weaknesses.
A．whatever
B．whichever
C．whenever
D．however
A．5A
B．5A
C．5/2A
D．/2A
A
/2
/2A