题目内容：

短文改错

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：把缺词处加个漏字符号（∧），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；  2. 只允许修改10处，多者（从第11处起）不计分。

More and more families are now rich enough to have their own cars. Cars do benefit the families as well the society in many ways. With a car, this is convenient for the family members to travel to or from work. They can also drive to the countryside on the weekends. At the same time, the development of motor industry will sure give a push to many other related industries, it is obviously beneficial to the social economy. On the other hand, the boom of private cars is also causing traffic and environmental problem. Waste gases from cars are causing serious pollution to the air, which do great harm to people’s health. With an increased number of cars on the roads, the traffic has become very heavily.