A:prefer
B:want
C:enjoy
D:mi
选项
物质(括号内杂质)
除杂方法
A
Cu(CuO)
加入适量的稀盐酸,过滤,洗涤和干燥
B
固体KCl(MnO2)
加水溶解过滤,洗涤,蒸发
C
NaOH(Na2CO3)
加稀盐酸,蒸发
D
BaCl2溶液(HCl)
加入过量的Ba(OH)2溶液
树木对人类的益处:防止水土流失、可以制造氧气、隔离噪音、净化空气、吸收有毒有害气体。( )
数位顺序表中每两个计数单位之间的进率都是10.
It was only after he had read the papers ________ Mr. Gross realized the task before him was extremely difficult to complete.