题目

一个基因型AaBb的卵原细胞，减数分裂产生一个Ab的卵细胞，与此同时产生的3个极体的基因型是 A．AB、ab、ab B．Ab、aB、aB C．aB、Ab、Ab D．AB、ab、aB 答案：B17、A small number of girls ________ under the tree now． A．played games                                   B．are playing games C．is playing games                                 D．play games