Concept:Carbonaceous sedimentary rocks are formed mainly from the remains of plants.
Explanation:These rocks contain a high proportion of carbon.
They develop when thick layers of vegetation get buried and compressed for long periods.
Heat and pressure gradually turn the plant matter into carbon-rich deposits.
Coal is the best example of a carbonaceous sedimentary rock formed in this way.
Such rocks are therefore not derived from tropical heat, molten magma, or coral remains.
Hence, the material that makes them up is vegetable matter.
Answer:C. Vegetable matter