题目内容：

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。

Last Sunday, my family went for walk in a nearby park. We wanted to breathe the fresh air and having fun there. However, when going out，we find it was cloudy and smoggy. Only a few people were walking quick on the streets wearing their masks. I was wondering why the matter was when my little brother began to cough loudly. Suddenly I realized that it was air pollution. So we had to go to home that day. Smoke from cars, buses, and factories make the air dirty，that is harmful to our health. I think they all should do some thing to keep the air clean.