Which of the following statements about the K-T boundary are true? (Note: More than one answer is correct.)
A. The K-T boundary is marked by a thin layer of clay found only in Gubbio, Italy.
B. The K-T boundary separates rock layers of the Cretaceous period from those of the
Tertiary period.
C. The K-T boundary dates to about 65 million years ago, when the dinosaurs
disappeared.
D. The K-T boundary in Zumaia, Spain, shows an abrupt change in the marine
ecosystem