Question

Fossil fuels are rich in carbon and:
A. Nitrogen
B. Oxygen
C. Sulphur
D. Hydrogen

Answer 1

Fossils are remains, traces of organisms that existed in the past. They are considered as written documents of evolution. Fossils occur in sedimentary rocks, peat, volcanic ash, amber, ice, asphalt, etc. Palaeontology or palaeobiology is the study of past life based on fossils. The study is divided into two branches, Palaeozoology (zoology of past animals) and palaeobotany (botany of past plants).

Complete answer:
Types of fossils:
Unaltered remains: At times dead bodies get embedded in materials where they do not undergo any change Examples of unaltered remains are ice, asphalt, amber, oil.
Skeletal materials: They are perfect fossils of hard and resistant structures like spore walls, teeth, bones and chitinous exoskeletons.
Petrifications: In these fossils organic materials are replaced slowly into mineral depositions.
Impressions: They are external features left over the hardened rocky matter after the decay of organic remains.
Organic molecules: Oil, Coal.
Now, we shall consider the given options :
Nitrogen: Two major fossil fuels, coal and oil contain nitrogen. Combustion of these fossil fuels produces both thermal and fuel nitrogen oxides.
Oxygen: The oxygen content of petroleum is typically in the order of 0.1–1.0% w/w.
Sulphur: In all fossil fuels Sulphur is present in diverse forms and to varying concentrations. In fossil fuel Sulphur is found in elemental form, in molecular form and as hydrogen sulfide gas ($H_2S$).
Hydrogen: Fossil fuels are rich in carbon and hydrogen. Majority of hydrogen is produced from fossil fuels by partial oxidation of methane and coal gasification or steam reforming. Only a small quantity by other routes such as electrolysis of water and biomass gasification.

So, the correct answer is option (D).

Note:
The process of formation of fossils is called fossilisation. There are some problems with fossilisation. Over land it is a rare phenomenon and occurs only when there are earthquakes, landslides, volcano eruptions, avalanches, etc. Mostly occur at the bottom of large lakes and sea. Remains of most land organisms do not reach the water courses. Fossils embedded in deeper rocks are destroyed due to pressure and heat.