钢进行压力加工时，加热的主要目的是（）。
A．提高塑性，降低硬度
B．提高塑性，降低变形抗力
C．消除铸锭中的铸造缺陷
参考答案：B
I didn't understand ______ so I raised my hand to ask. [ ]
A.what my teacher says
B.what does my teacher say
C.what my teacher said
D.what did my teacher say
汽车差速器的作用是什么？
