下面的小学校园平面图是长方形，请根据这个平面图完成以下各题

一个原子核在中子的轰击下发生一种可能的裂变反应，其裂变方程为+,则下列叙述正确的是(    )

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。每处错误仅涉及一个单词的增加、删除或修改。

增加：在缺词处加一个漏字符号（ $\wedge$ ），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：在错的词下画一横线，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。

    The annual English Festival, which was lasted one week, has just ended. There were all kinds of colorful activities, included an English speech competition. Last Friday, we had an honor of inviting Professor Smith to deliver a lecture on English cultural background information, such as English idiom. He was very learned and humorous that he began his lecture with an amusing story to attract the attention of the audience and all of us was deeply impressed with his wisdom. We admired him and took notes carefully, for he made himself understood with speaking slowly and clearly enough for us to follow her. He gave us some practically ways to develop the sense of language and encouraged us to keep speaking English as much possible in our daily life.

因式分解：x²﹣2x+1=____．