— _________ do you play the piano? — Once a week.[ ]
A. How
B. What
C. How often
答案:C
中药贮藏不当可能引起的变质现象()
A.霉变
B.虫蛀
C.走油
D.起霜
E.风化
矿渣硅酸盐水泥中混合材总掺加量按质量百分比计为()。
A.10-15%
B.15-50%
C.20-70%