处语言错误，每句中最多有两处。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(＼)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。

    Recently, our class have had a heated discussion concerning that whether the Beijing Zoo should be moved out of the city. Some of my classmates approved of the moving .They say large crowds of tourist to the zoo will result in traffic jams .They also say that once moving, animals will have more space and good living conditions in the suburbs. Therefore, other students against the idea. They say that the zoo has the history of 100 years, and is famous at home or abroad. Moreover, moving may cause the dead of some animals. So, it's a better choice to remain where it is.

与酸雨形成相关的气体主要是（    ）