题目

对于下面制备单克隆抗体过程示意图，不正确的叙述是( ) A．①表示B淋巴细胞和骨髓瘤细胞均是从小鼠的脾脏中提取的 B．④中的筛选是通过抗原、抗体反应进行的 C．②促进细胞融合的方法可以利用聚乙二醇作介导 D．⑤可以无限增殖 答案：AIf the south had won the war,________ is now the United States might have been divided into several countries. A. what            B. where C. then            D. that