Question

what stage of coal formation takes place very deep underground, where the coal is formed by really high pressure and temperature? peat coal lignite coal source material bituminous coal

Explanation:

Coal formation stages: Peat is early stage (low pressure/temperature). Lignite is next (higher than peat). Source material is initial organic matter. Bituminous coal forms under very high pressure/temperature deep underground.

Answer:

bituminous coal