1950年6月《人民日报》发表社论称：“这是一件翻天覆地的大事”，是“中国人民对残余的封建制度所发动的一场最猛烈的经济政治战争，将在实际上结束中国社会的半封建性质。”这件大事应是（    ）

如图所示是某型号的水陆两用坦克，它的车体比普通坦克要大，呈船形，既能在陆地行驶，也能在水中浮动．该水陆两用坦克的总质量是2.2×10⁴kg，每条履带的触地面积是2m²，发动机功率是4.2×10⁵W，水上最大速度14km/h，陆地最大速度54km/h．请根据以上信息求解该坦克：（g=10N/kg）

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；

    Your problem is common one among middle school students. Maybe the following advices can help you. First in all, believe in yourself. Your greatest problem is that you lack(缺少) self-confidence. The first thing you must do is to smile at your classmate. One smile speaks loud about your wish to make friends than any word. Your smile will show that you are friendly to him. Next, trying talking with a student who is as shy as you or who share the same interest as you. You can discuss your studies with a classmate, and you can also talk about your hobbies as well. Unless anyone is in trouble, you should be ready to help him or her. Once you have confidence, you can make as many friends as possibly.

如图所示是两磁极间磁感线的分布图。下列关于两个磁极的说法正确的是（   ）