A:in America
B:one in America
C:America
D:that in America
例:I like pears.→ I don't like pears.
边长为2 cm的正方体物块,静止在水中,上下表面水平.物块上表面在水面下8 cm,下表面离水底1cm.已知水的密度为 1.0×103kg/m3 .请计算: