My mum does ______ housework every day. [ ]
A. many
B. much
C. any
D. a lots of
答案:B
下列说法正确的是( )
A.NaCl是电解质,所以NaCl可以导电
B.CO2能溶于水,且水溶液能导电,所以CO2是电解质
C.BaSO4难溶于水,故将BaSO4放入水中存在电离平衡
D.NaHCO3仅能在水溶液中导电
甲、乙两个实心铁球,已知甲、乙两球的质量分别是2kg和6kg,则甲、乙两球的体积之比为______,密度之比为______.