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短文。短文中共有10处错误，每句中最多有两处。错误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(∧), 并在此符号下面写出该加的词。

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。

            My brother Donald didn’t do well in math. When the day of theexam comes, Donald sat next to Brian, which was always good at math. Donaldcareful copied Brian’s answers. At end of the exam, the teacher collected thepapers and graded it. Then she decided to give a prize to the student who gotthe high grade. But it was a bit of difficult for her to make a decision,because Donald and Brian got the same grade. The teacher thought about that andmade on her mind to give the prize to Brian. Donald said it was unfair. “That’strue,” the teacher said. “Therefore, Brian’s answer to Question 18 was ‘I don’tknow’. Your was ‘Neither do I’.”

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手机已经成为了人们日常必备品之一，低头看手机的“低头族”随处可见（图甲）．有研究发现，若玩手机时姿势不当，可能让颈椎承受多达27公斤的重压．为求证这一问题，某同学查阅相关资料，画出了“低头族”头部前倾某一角度时的模型（图乙），颈椎看成轻杆，颈部肌肉看成轻绳，头部看成质点，所受重力已标出．请在答卷的图丙中用平行四边形定则作出重力与颈部肌肉对头部拉力的合力，并根据所作的图测量颈椎承受的压力是头部重力的倍．（保留两位有效数字）

无论m为何实数，直线y=x+2m与y=－x+3的交点不可能在(     )