Coal is formed when

O

A

sediments cover dead marine organisms and heat converts them into complex, energy-rich carbon molecules.

O

B

deposits of methane are subjected to high pressure until they condense into crystals.

swamplands are buried by sediment. The added weight creates heat and pressure that converts the plants to coal.

Oo

organic remains get trapped in nonporous rock and merge into large bodies of complex, energy-rich carbon molecules.