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。
"Practice makes perfect" was an old saying.It tells us that it does not any matter if we are slow at doing something.As long as we keep on trying and practice,we'll do a good job at the end.The saying is especial useful in English study.Since a student is poor at speaking,he should catch every chance to open mouth and speak English.His oral English may be excellent one day as a result of his hard works.Not only is the saying useful in English study,but it is helpful in our daily life as well.To some degree,it is no easy way in doing everything since the key to succeed lies in "Practice makes perfect".
关于点O对称，下列结论不正确的是（ ）.