李伟在实验室药品柜中发现一瓶标签残缺的无色溶液（如图），老师告诉他这是实验室常用的试剂．这瓶溶液可能是（　　）

发达国家人口增长慢的原因是（    ）

阅读短文，判断正（正确）误（错误）

     Dick was not old, but he does not have much hair. His wife Emma has thick, beautiful black hair. They have a son. His name is Peter, and he is five years old. One day, Dick was reading a book in his study. Peter looked at his father for a long time and then said to his mother, “Why does Papa have so little hair, Mama?” Emma laughed and said, “ He has little hair because he thinks a lot. He's a very clever man.” Peter looked at his mother's thick black hair for a few seconds and then said, “Then I know why you have so much hair.”