下列物质属于电解质的是[ ]
A. CO2
B. CH4
C. Na2SO4
D. Cu
答案:C
某市在一次扶贫助残活动中,共捐款2580000元.用科学记数法表示为( )元.
You____________ television. Why not do something more active?
A.always watch
B.are always watching
C.have always watched
D.have always been watching