Which of the following statements about scientists' theories on the extinction of the dinosaurs can be inferred from paragraph 2? A. Some scientists do not believe that an asteroid or comet impact killed the dinosaurs. B. Some scientists think that iridium was abundant on Earth before the extinction of the dinosaurs. C. Some scientists doubt that all of the dinosaurs died out 65 million years ago. D. Some scientists believe that the dinosaurs became extinct only after the plants and animals they ate disappeared.