In paragraph 4, all the following questions are answered EXCEPT: A. Why is there a layer of clay between the rocks of the Cretaceous and Cenozoic? B. Why were scientists interested in determining how long it took to deposit the layer of clay at the end of the Cretaceous? C. What was the effect of the surprising observation scientists made? D. Why did scientists want more information about the dinosaur extinctions at the end of the Cretaceous?