What is a possible effect of crossing animals that belong to different special

We live in the cenozoic era, and scientists know more about this era and the epochs it's divided into than any other time period. why is this? a. we know more about the cenozoic era because this is the only era that has had a wide diversity of species living on earth. b. we know more about the cenozoic era because the planet's poles reversed magnetic fields at the beginning of this era. c. we know more about the cenozoic era because fossils don't exist to document previous eras. d. we know more about the cenozoic era because this is the most recent time period in the history of the earth, and we have more information available to study.