题目

  Should the color be white or black? Or perhaps navy blue! Well，choosing the right graduation dress for middle school students can be a little difficult at times. Here are some ideas for graduation dress for middle school students．     For many students，middle school graduation marks a big change in their lives．This is a step that takes students away from junior high school but towards the elementary level before senior high school．Compared to elementary(初级的)school，middle school means more lessons and more classes，but of course，students can also see it as an 两个相同的圆柱形容器放在水平桌面上，分别盛有质量相等的酒精和水．把甲、乙两个金属球分别浸没于酒精和水中（已知液体不溢出，ρ酒精＜ρ水），此时，液体对容器底的压强相等，容器对水平桌面的压强也相等．以下说法正确的是（ ）A. 甲球质量小于乙球质量 B. 甲球质量大于乙球质量C. 甲球密度小于乙球密度 D. 甲球密度大于乙球密度