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
