选出不同类的一项（  ）

根据所给汉语意思及文章内容，写出单词的正确形式。（每空限填一词）

    Oliver Twist is a famous novel ____(写) by Charles Dickens. It mainly talks about the boy named Oliver Twist. His parents  ____(死), he has to grow up with many poor ____ (陌生人). One day, when nobody pays ____(关注) to him, he runs away in a ____ (仓促) to London. After he gets to London, he is cheated by one bad guy called Fagin who is very ____ (不礼貌的)and then he starts his life of ____ (偷). In Fagin's house, Oliver also meets some good partners who really care about him. When Oliver is taken to the police station, a good man  saves him and is quite ____ (耐心的) with him. He teaches Oliver how to read books, how to learn ____ (明智的) and how to be a gentleman. These abilities are very ____（有帮助的）to him. More importantly, Oliver's happy childhood has finally come to an end

胚胎干细胞（ES细胞）在生物学研究中具有十分重要的应用价值．

（1）图为某科研小组采用“基因靶向”技术先将小鼠的棕褐毛色基因导入黑色纯种小鼠的ES细胞中，再将改造后的ES细胞移植回囊胚继续发育成小鼠的过程．在目的基因获取和基因表达载体构建过程中使用的工具酶有____ ．

（2）图中完成第Ⅱ步操作得到由两个DNA切段连接成的产物有____ 种重组DNA分子；第Ⅲ步操作后，还需经过____ 的过程，才能将该ES细胞注射到囊胚中．

（3）ES细胞在功能上具有____ 的特点；目前研究人员正尝试通过科技手段利用ES细胞经过特殊诱导，为因故失去手的患者提供新的“手”，该过程揭示了细胞____ 的机理．

（4）已知细胞合成DNA有D和S两条途径，其中D途径能被氨基嘌呤阻断，一般情况下，细胞中有D或S途径即能分裂增殖．人淋巴细胞中虽然有这两种DNA合成途径，但一般不分裂增殖．鼠ES细胞中只有D途径，但能不断分裂增殖．将这两种细胞在试管中混合，加____ 促融，获得杂种细胞．若要从培养液中分离出杂种细胞，写出实验方法（不考虑机械方法），并说明理由．

方法：____．

理由：____ ．