A:1
B:1或 32
C:1, 32 或± 3
D:3
一个基因型为AaBbCc的精原细胞,减数分裂形成4个精子,这四个精子的染色体组成可能是( )
如图所示,杠杆在水平位置平衡,做下列调整后杠杆仍然能平衡的是 ( )
多项式1+2xy﹣3xy2的次数为( )
—Did you go to her birthday party? —I __________, but I had to work extra hours to finish my homework.