疏水阀的作用是()
A.排水
B.排气
C.排水阻气
D.排气阻水
参考答案:C
一What______he______?
一He is of medium height. He has curly hair and wears glasses.[ ]
A. does; like
B. is; like
C. does; look like
D. does; look
下列各组金属中,最适合用H2或CO把它们从其对应的化合物中还原出来的是( )
A.K、Mg
B.Al、Fe
C.Fe、Cu
D.Hg、Ag