题目内容：

短文改错

文中共有5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（\）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5处，多者（从第6处起）不计分

A group of scientists were planning to go to the countryside to do a scientific research in order to find out that whether the environment of the country had polluted. On arrival , they started to check the air and water. To our surprise , they found how terribly the situation was. They could see the serious pollution. Looking into the cause, they persuade the government to pass the law to protect the environment and kept the balance of nature . Now everything has changed. Birds are singing while trees and grass are waving .