当小汽机真空下降至()kPa,跳闸保护应动作,若保护拒动应不破坏真空紧急停机。
参考答案:-60
This was the first time that Chongqing the Listening Examination of Public English Test System II (PETS-2).
A.has joined
B.joined
C.will join
D.had joined