机械除锈法主要有手工除锈，手动和电动工具除锈、（）除锈。
A.喷丸
B.化学
C.喷砂
D.打磨
参考答案：A
—How nice your bike is! How long ____ you it ？
—For two weeks.[ ]
A. have; bought
B. have; had
C. did; buy
提取分离强心苷要注意哪些问题？
