题目

阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。Learning a foreign language is a challenging task，【1】 it can also be a very enjoyable experience.Here are a few 【2】(tip) on how to learn a foreign language well.Firstly，work on your own pace.You'll find 【3】more effective to study for half an hour rather than try to do a whole unit at once.Secondly，use language【4】(communicate)．Don't worry about 【5】(get) things wrong.The important thing is to build up your 【6】(confident) in speaking.Thirdly，build up your vocabulary.You 将抗虫棉的基因导入到受体细胞后，发生了如图过程：此过程中用到的条件包括（　　）①解旋酶　   ②DNA聚合酶　  ③DNA连接酶　  ④限制酶　⑤RNA聚合酶  ⑥4种核苷酸　  ⑦5种核苷酸　  ⑧8种核苷酸． A、②⑤⑥B、①⑤⑥C、①⑤⑦D、④⑤⑥