浮力计算的普遍公式是( )
A:F浮=ρ液gV排
B:F浮=G物
C:F浮=F1﹣F2
D:F=F向下﹣F向上
缺钙或缺乏维生素D容易患( )
—I'm sorry to hear that. You ______ be very sad.