The correct option is C peat
Peat is an organic sediment. Burial, compaction, and coalification will transform it into coal, a rock. It has a carbon content of less than 60% on a dry ash-free basis.
Peat forms when plant material does not fully decay in acidic
and anaerobic conditions. It is composed mainly of wetland vegetation:
principally bog plants including mosses, sedges, and shrubs. As it
accumulates, the peat holds water.