研磨工具与工件之间，两者不受外力的强制性引导，而处于（）状态
A、窜动
B、震动
C、浮动
D、摆动
参考答案：C
看图完成答句，一空一词。
1. Where are the boys?
They are ________ the ________.
2. What are one group of the boys doing?
They are _________________________.
3. What are the other group of boys doing?
4. Where are the three students standing?
They are standing ________ a big ________.
5. What are they doing?
They're ________ the basketball ________.
攻螺纹时，对铸件要加（）。
A、煤油
B、机油
C、汽油
D、洗油
