蜗杆传动是指蜗杆和蜗轮的啮合传动。( )
参考答案：对
转向架构架、侧架、摇枕等大型零件采用加热调修变形时的加热温度应控制在（）℃。
The little boy ate a big meal he said he wasn't hungry. [ ]
A. if
B. though
C. because
D. as
