A:So what
B:Why not
C:How come
D:What for
There ____ a full bin yesterday. But there is an empty one now.
用亲本基因型为DD和dd的植株进行杂交,对其子一代的幼苗用秋水仙素处理产生了多倍体,其基因型是( )
据右图,资本主义世界工业发展速度在1870年后发生显著变化,其决定因素是 ( )