三个实数成等差数列，首项是9，若将第二项加2、第三项加20可使得这三个数依次构成等比数列$\left\{a_n\right\}$，则$a_3$的所有取值中的最小值是（ ）

 某化学实验小组加热15.5gKClO₃和MnO₂的混合物制取氧气，完全反应后，称得固体剩余物质量为10.7g．请计算：

    I get up at 6: 50 every morning. Then I put on my clothes and shoes. And I eat my breakfast at 7: 20. I have milk, apple and bread for my breakfast. I go to school by bus. I arrive at school at 8: 00. Then I have my lesson at 8: 20. I go home at 5: 30 after school.

计算-1+1的结果是（　　）