题目

科学家利用胚胎干细胞在实验室中培育出了“微型人脑”组织，下列叙述正确的（） A . 该过程不会发生细胞衰老 B . 该过程中细胞会发生程序性死亡 C . 该实验体现了动物细胞的全能性 D . 该过程遗传物质会发生改变并引起细胞分化 答案：B They asked me to have a drink with them．I said it was at least five years since I ________ a good drink． [　　] A．had enjoyed B．was enjoying C．have enjoyed D．have been enjoyed