全列车空气制动的控制机构是（），通过对其手柄的操纵，实现制动机的各种性能和作用。
A.分配阀
B.作用阀
C.自动制动阀
D.单独制动阀
参考答案：C
---Tom’s been sent to the USA for further study. What about his twin sister?
--- _____.How lucky they are!
A．So has she
B．She is too
C．So is she
D．So she has
进行作业准备验证的时机：（）
A.生产启动时
B.顾客有要求时
C.按照控制计划规定
D.不需要验证
