闭式网络只有在相位相同时才允许合环.
参考答案：对
This is the second time Nie Haisheng ________ to be the astronaut who took the glorious task.
A．has been chosen
B．had been chosen
C．was chosen
D．chose
属于嗜盐性细菌的为（）
A.空肠弯曲菌
B.霍乱弧菌
C.铜绿假单胞菌
D.副溶血弧菌
E.痢疾杆菌
