With the changes in the world's climate, dinosaurs died, but many smaller animals lived on. It was the survival of the fittest. 随着世界气候的变迁,恐龙绝迹了,但许多较小的动物却继续活了下来。 这就是适者生存。
牛津高阶第八版
美国韦氏词典
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维基百科 (自由的百科全书)