题目内容：

下面短文中有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：在缺词处加一个漏词符号（∧），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。

A century before, a bird called the passenger pigeon lived in North America. There were so many passenger pigeons when people often saw thousands, even millions of birds flying overhead. Therefore, there is not a single one left today. What happened? How did all passenger pigeons disappear from the earth entire?

The passenger pigeons become extinct for two reason. First, the forests that it lived was cut down to make way with farms and cities. Second, many pigeons were shot and eaten because they were good to eat. At that time, there were no hunting laws protect endangered species as they are now.