Answer:
HUGE SWAMPS
Explanation:
Back then, much of the earth was covered by huge swamps. They were filled with giant ferns and plants. As the plants died, they sank to the bottom of the swamps. Over the years, thick layers of plants were covered by dirt and
water. They were packed down by the weight. After a long time, the
heat and pressure changed the plants into coal.
Hope this helps :3
