A:甲物质的密度为1.5×103kg/m3
B:甲物质的密度小于乙物质的密度
C:乙物质的密度小于0.75g/cm3
D:30mL甲物质的质量为45g
Mike used to be a top student, but he ______ behind since he lost himself in computer games.
青春期发育的突出特征是生殖器官的发育和成熟.