选项
筛选前
第一次筛选获得
第二次筛选获得
A
a、aa、ab、bb、b
a、aa、ab
ab
B
ab、bb、b
C
能无限增殖的ab
D
能产生特定抗体的ab
—I haven't worked the problem out yet. What am I supposed to do?
—Try again! It’s only difficult.