Answer:
D. Time and pressure changes dead plant material to peat.
Step-by-step explanation:
There are four steps in the production of coal: peat, lignite, bituminous and anthracite.
Peat: in this stage dead plants are oxidized to water and carbon dioxide and buried under sediments. The partial decomposition of plant matter due to the absence of oxygen is called peat. There is no factor of time and pressure that changes dead plant material to peat.
Lignite: Peat is subjected to heat, pressure, and time to form lignite.
Bituminous: More pressure in lignite removes all the traces of plant matter and form “soft coal”, bituminous coal.
Anthracite: It is the last stage, in which hard coal forms with the combined pressure and high temperature.
Hence, the correct answer is "D. Time and pressure changes dead plant material to peat."