周长=____

周长=____

我国有四大地理区域，下列有关西北地区地理环境特点的叙述正确的是（　　）

    Hello, my name is Gina. John, Anna and I are good friends. We are in the same grade (年级). But they are in Class Five and I am in Class Three. We get up at 7:00 and go to school at 7:30. In the morning we have four lessons. We have English every morning. John and Anna have English at 10:00 in the morning and I have it at 11:00. English is my favorite subject. Math is their favorite. And we all like P.E.

    In the afternoon, we have three lessons. At 2:30 we have the art lesson in the same classroom. After school we often play soccer. We all like soccer. Sometimes (有时) we watch TV at my house. We don't play any computer games.

根据短文内容，选择正确答案。

硫酸厂的污水中含有硫酸排放会导致河流水质酸化，加入下列物质不能解决问题的是（   ）

历史证明，科技与经济的创新和杰出的人物是推动社会发展的重要动力，但也会产生负面的影响。