Answer
c.
Work Step by Step
The Carboniferous period, which is the time when coal-forming forests appeared and flourished, is part of the latter portion of the Paleozoic era. The Carboniferous period began about 359 million years ago and ended about 299 million years ago. The Paleozoic era began about 542 million years ago and ended about 251 million years ago. Therefore, the Carboniferous period lay within the Paleozoic era.