蝗灾是重要的生物灾害之一，它们不仅危害农作物和农田，还对草场造成严重威胁。据此完成：

有关我国蝗灾的叙述，正确的是(   )

①我国历史上造成过重大灾难的害虫首推蝗虫②由于农业现代化的发展，20世纪90年代以来，我国蝗灾已基本消灭③由于蝗虫有远距离迁飞特征，因而不能用飞机来灭蝗

④历史上蝗灾曾经与水灾、旱灾一起并称为三大自然灾害

下图所示历史事件中，标志着抗日民族统一战线正式形成的是（    ）

东西半球的分界线是（　　）

发现行星运动定律的科学家是

假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。每处错误仅涉及二个单词的增加、删除或修改。
增加：在缺词处加一个漏字符号(∧)，并在其下面写出该加的词。
删除：把多余的词用斜线（\）划掉。
修改：在错的词下划一横线，并在该词下面写出修改后的词。
注意：1）每处错误及其修改均仅限一词；
      2）只允许修改10处，多者（从第11处起）不计分。
    I will share with you true story that happened a couple of day ago. One of my classmates bought a bag of snacks from a food store. A few classmates were then inviting to enjoy the snacks. Unluckily, all of us got poisoned and had stomachaches with their faces pale. They were quickly sent to a nearby hospital. Doctors examined them but gave them some medicine. They were out of danger soon before taking the medicine. This accident makes us to realize the seriousness of the food safe problem. Therefore, I strong suggest that the whole society pays more attention to it.