进入鱼体和流出鱼体的水中，溶解的气体成分有什么变化？请根据以下提示设计实验进行证明。
提示：溴麝香草酚蓝简称BTB，遇二氧化碳后，BTB溶液的颜色会由蓝色变成黄色。短时间内使用BTB对鱼没有影响。

请阅读下面短文，根据其内容，用方框中所给单词的适当形式填空。(每个单词限用一次)

Li Wen is a 16-year-old boy. He works hard and ____  well in school. It is hard to believe that he used to have much ____ in school. His parents moved to the city to look for jobs. ____  they couldn't be at home to 1ook ____ him. From then on. he became less interested in ____to school and missed classes. Then his parents made a ____  to send him to a boarding school. He was shy and had no friends. Life there was difficult for him. One day he told his teacher he wanted to____  the school. His teacher called his parents md advised them to come back and talk with their son in person. Then his parents came back and had a talk with him. This ____changed his life. He realized that his parents would always love him and they would be ____ of everything good that he did. Now he is much____ and more outgoing than he used to be.

有关如图的叙述，正确的是（    ）

（1）①→②表示DNA转录（2）共有5种碱基（3）①②中的A表示同一种核苷酸（4）共有4个密码子（5）①→②过程主要在细胞核中进行．

下框材料选自民国二十二年第二期《申报月刊》。这阐述的“统制经济”思想在当时的中国影响较大，其客观因素是