泵在启动时干摩擦会造成机械密封损坏。
参考答案：对
Hasn't the train ? [ ]
A. got to
B, reached
C. arrived at
D. arrived
清炖蟹粉狮子头时不能添加______一起炖制。
A．螃蟹肉
B．香菇块
C．笋
D．排骨
