Final answer:
The correct chronological order of the geologic eras is Paleozoic, followed by Mesozoic, and Cenozoic, corresponding to Option A of the choices provided to the student.
Step-by-step explanation:
The correct order of the geologic eras, from most ancient to most recent, is Paleozoic, Mesozoic, and Cenozoic. Option A is the right choice.
The Paleozoic Era is recognized as the era of "old life" and spanned from about 541 to 252 million years ago, undergoing significant events such as the Cambrian explosion and the Permian extinction.
Following the Paleozoic, the Mesozoic Era, known as the Age of Reptiles or Dinosaurs, lasted from 252 to 66 million years ago. It was marked by the breakup of the supercontinent Pangaea and witnessed the dominance of dinosaurs.
Finally, the Cenozoic Era extends from 66 million years ago to the present, following the mass extinction event that closed the Mesozoic Era. It is divided into several periods up to the current Quaternary period, which includes the Holocene Epoch that we live in today.
Hence, option a is correct.