Why does the author include the information that dinosaurs had flourished for tens of millions of years and then suddenly disappeared?

• A. To explain why paleontologists have always been intrigued by the mass extinction at the end of the Cretaceous period
• B. To support the claim that the mass extinction at the end of the Cretaceous period is the best-documented of the dozen or so mass extinctions in the geological record
• C. To explain why and how as many as half of the species on Earth at the time are believed to have become extinct at the end of the Cretaceous period
• D. To provide evidence that an impact can be large enough to disturb the environment of the entire planet and cause an ecological disaster