发动机启动后不能立即投入工作，应让发动机在无负荷状态下半速运行（）分钟左右。
A.1
B.5
C.10
D.15
参考答案：B
You_____make such mistakes again.
A．should never
B．should not always
C．would always not
D．would not forever
改善轧件咬入条件有哪些方法？
