逆转录
参考答案：以RNA为模板合成DNA的过程。
With all his attention ____ on the computer game, the boy even didn't notice his mother came in.
A．was fixing
B．was fixed
C．fixing
D．fixed
《喂——出来》作者在文章结尾设计“声音”、“石子”又回来了，有怎样的用意？
答：________________________________________________
