直输机水泵轴承为（）轴承。
A.圆柱滚子
B.深沟球
C.调心球
D.滚针
参考答案：B
将下列句子变为一般疑问句，并作简要的肯定回答和否定回答。
1. This is Gina.
_________________
2. That is his brother.
3. He is my good friend.
4. These are nice pictures.
5. Those are school things.
什么叫采样单元，多少为一个基本采样单元？
