The planet has not seen such a spasm of extinction in sixty-five million years, since the dinosaurs disappeared. (Unit 10: The World We Have Lost)Which of the following best explains the meaning of the sentence?
选项：

A:A great number of species have replaced other species since the dinosaurs became extinct sixty-five million years ago. ;
B:The rate of species extinction has been increasing since the disappearance of the dinosaurs sixty-five million years ago.;
C:The world has not experienced such a great number of species extinction since the disappearance of the dinosaurs sixty-five million years ago.;
D:The disappearance of dinosaurs sixty-five million years ago was the greatest calamity on the planet.