Everyone likes living in a clean and comfortable environment. If the envionment(环境) is bad, it will affect（影响）our bodies, and make us not feel well. Sometimes we may be terribly ill. At that time we don't want to work, and we have to stay in bed and rest at home. So the envrionment is very important to us.
      It's germ that makes us ill. There are germs everywhere, They are very small and you can't find them with your own eyes, but you can see them with a microscope（显微镜）. They are very small and there may be hundreds of them on a very small thing, Germs can always be found in the dirty water. When we look at dirty water under the microscope, we shall see them in it. Germs can also be found in air and dust（灰尘）. If you cut your finger, some of the dust from the floor may go into it, and you will have much pain in it. Sometimes the germs will go into all of your boby, and you will have pain everywhere.
     To keep us healthy, we should try to our best to make our environment become cleaner and tidier. This needs us to act together.

不是…… 而是…… 虽然……但是…… 与其…… 不如…… 只有……才……

①____“我为人人”，____会实现“人人为我”的美好愿望。

②____我离开德国多年，____德国的美丽从未改变。

③德国人的花儿____养在屋子里，____种在临街窗户的外面。

④____自己欣赏美好的事物，____和大家一起分享。

其中 $t_i=x_i{}^2$ ， $\overline{t}=\frac{1}{7}{\displaystyle \sum }_{i=1}^7{t}_i$ ，z_i=lny_i， $\overline{z}=\frac{1}{7}{\displaystyle \sum }_{i=1}^7{z}_i$ ，

附：对于一组数据（μ₁，ν₁），（μ₂，ν₂），（μ_n，ν_n），其回归直线v=βμ+α的斜率和截距的最小二乘估计分别为： $\beta =\frac{{{\displaystyle \sum }}_{i=1}^n\left({\mu }_i-\overline{\mu }\right)\left({\nu }_i-\overline{\nu }\right)}{{{\displaystyle \sum }}_{i=1}^n{\left({\mu }_i-\overline{\mu }\right)}^2}$ ， $\alpha =\overline{\nu }-\beta \overline{\mu }$

下列说法正确的是（  ）