客车空调机组的电预热器所设置的温度开关式电热保护器断开值是（）℃。
A.70±5
B.80±5
C.90±5
D.100±5
参考答案：A
.It is said that pandas ___________ in our country year after year.
A．are being disappeared
B．are disappearing
C．will be disappeared
D．will disappear
当球磨机的直径一定时，筒体越长，磨机生产率（）。
A、越高
B、越低
C、不变
