Incomplete decomposition of organic matter due to a lack of oxygen. (Ans D).
Explanation:
Coal is known as the mostly carbon with containing different amounts of oxygen, nitrogen, sulfur, and hydrogen. Coal is formed when Incomplete decomposition of dead plant matter due to a lack of oxygen occurs. In-plant matter because of the pressure, and heat-generating physical, and chemical changes occur which lead to force out oxygen, and carbon deposits left. so, in this time the plant matters become coal.
Coal is divided into three main types which are based on the percentage of hydrocarbon, oxygen, and carbon occurs in the coal.
