The correct answer is option B, Oil Shales
Oil shales are sedimentary rocks with fine grains and belong to the group of Sapropel fuels. They are usually found in shallow marine lagoons and lakes. The oil shales dominate in organic matter such as algal material and some plant origin. Marl on the other hand is mudstone enriched in lime and carbonates of calcite. Within the lithology, a mixture of organic and inorganic material exists coherently including shales, marls, and carbonate rocks, organic remains etc.