正常男性体细胞的染色体组成是( )
A:23对+X
B:22对+XY
C:23对+Y
D:22对+XX
—Where are my model planes, mom? —Sorry, I don't know. Oh, look, they are _________.
The girls ______ how to dance a month ago and now they can dance well.
有一量杯,它的最大刻度值是100cm3,最大刻度线距离杯底的高度为h,则在高度为h/2处的刻度线表示容积的数值是( )
如图所示,在水平地面上用F1水平拉动质量为m的物体匀速运动x所做的功为W1,第二次用与水平地面成θ的F2拉动同一物体匀速运动x所做的功为W2;则有( )