短文改错（共10小题；每小题1分，满分10分）
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。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。
One hundred and forty million years before human being existed, dinosaurs ruled earth.
They lived for such long on the earth that they developed into many different species. They had few enemies beside each other, so each species had to protect their young from been eaten by other dinosaurs. As they lived in a warm and wet climate, there were plenty of food, so dinosaur species multiply quickly. Who knows what would have happened if the earth’s weather had not changed? Sad it became hot and dry and the dinosaurs were unable to prevent them from disappearing altogether. It is still a mystery that why they suddenly became extinct.
However, students and scientists love to study their bones and imagine their life so they can solve the mystery in the future.