barren deserts active volcanoes mountains covered in trees swamps with dense vegetation
I gave my students this multiple choice question: The formation of coal deposits occurred over millions of years. Which feature was most responsible for these deposits?

Only one answer is correct among these 4 choices:
- barren deserts
- active volcanoes
- mountains covered in trees
- swamps with dense vegetation

Could you tell me which one is correct?

swamps with dense vegetation