Fire can be helpful to us if it is proper ways.
A、used to
B、used in
C、used for
D、used of

单项选择题In order to keep focused, you should not make your presentation _____________. A、 professional B、visual C、long D、close to the theme

单项选择题《中国药典》中富马酸亚铁的含量测定，药品前处理采用的方法是（ ）