A.CO2 B.SO2 C.HCl D.H2O E.N2 F.Ca(OH)2
—The player looks better because the coach has got her every day.
— Yes, practice makes perfect.
如图,BD是∠ABC的角平分线,AD⊥AB,AD=3,BC=5,则△BCD的面积为( )
某四倍体植物的某细胞核含20条染色体、20个DNA分子,且细胞中存在纺锤丝,则该细胞所处的时期与细胞中一个染色体组所包含的染色 体数分别是( )