Dinosaurs were once found all over the earth. Now they are gone. They have all died out. No one is sure how this happened. Some scientists believe the weather changed. Some believe disease killed them all. All that we can be sure of is that once they lived. 恐龙曾遍布地球的每个角落，现在他们没了，全部都灭绝了。没有人确定这是怎么发生的。一些科学家认为气候变了，还有一些认为是疾病导致它们灭绝。我们所能确定的就是它们曾经生存过。 编辑推荐：2009年下半年公共英语考试报名汇总 名师指导公共英语阅读考试技巧 公共英语pets三级全真模拟试卷 公共英语pets二级语法讲解汇总