A:Na2O2
B:KOH
C:CaCl2
D:CO2
小明在探究甲、乙两种不同物质的质量和体积的关系时,得出了如图所示的图象.由图象可知,甲、乙两种物质的密度之比ρ甲:ρ乙= ____.用甲、乙两种不同的物质做成质量相同的实心体,则它们的体积之比V甲:V乙= ____
There are __________ books on the desk.
---Jack, I'd like to have your opinions about my report.
---________. But I have one suggestion.