在胚胎工程中，转基因动物培育、核移植中都必须用到的两项技术是（    ）
①动物细胞培养　②克隆　③减数分裂　④胚胎移植

根据下列句子及所给汉语注释，在句子空缺处写出各单词的正确形式（每空只写一词）。
 There are about two ____ （百）students playing on the playground.
  The mother is ____ （自豪的）of her son, because he is very successful in his work.
 There are many kinds of English ____（字典）in this bookstore. You can choose the one you like.
  Look at the photo____ （仔细地），and you will find our teacher.
 Would you mind____（打开）the window? We need some fresh air.

在平行四边形ABCD中，M为$\overrightarrow{AB}$上任一点，则$\overrightarrow{AM}$-$\overrightarrow{DM}$+$\overrightarrow{DB}$等于（　　）

近年来发展起来的胚胎工程技术为优良种畜的快速繁殖带来了无限生机，下图为经体外受精和胚胎分割、移植培育优质奶牛的过程。下列相关叙述正确的是