Answer:
D. lignite
Step-by-step explanation:
The lignite is a type of coal. It is the type of coal that is ranked at the bottom by its heating capacity, as all other types of coal produce more heat than it. The percentage of carbon in this type of coal varies between 60 and 70%, which is actually the main reason why it produces the least amount of heat, as it has the lowest consistence of carbon. Because the carbon is in lower amount, this type of coal also has lighter coloration than the other types of coal. The lignite is an abundant sedimentary rock and it is found all over the world, unfortunately it is not of great usage.