Question

Coal is an example of ______________.
A. Igneous rock
B. Sedimentary rocks
C. Metamorphic rocks
D. None of the above

Answer 1

Hint: Coal is an extensively used fossil fuel. It is a hydrocarbon but contains oxygen, sulfur, and nitrogen along with a vast amount of carbon. This fossil fuel can be graded into three categories according to its carbon content: peat, bituminous, and anthracite.

Complete answer:
Rocks can be defined as naturally occurring aggregates of mineral and mineraloid contents. It can be classified into different categories based on the minerals they include, their chemical composition, and how they were formed.
Igneous rocks Igneous rocks are also called magmatic rocks which are formed due to the cooling of molten lava or magma. These might also be formed from crystallization to form crystals within the rocks. The molten lava can either crystalize within the earth’s surface or above it. When the magma solidifies below the surface it is called intrusive igneous rock and when it crystalizes above the surface, it is called extrusive igneous rock.
Sedimentary rocks These rocks were formed when the particles of minerals or organic materials settled on the rock beds and sea beds. Due to humongous pressure, these sediments were cemented to form rocks. When pteridophytes, forests, and swamps fell, they were buried under such sediments forming vast resources of hydrocarbons in millions of years. These hydrocarbons are used as fuels and are known as fossil fuels. Example: Coal, petrol.

Thus, option (B) is correct.

Note:The fossils of dinosaurs, extinct plants, and animals are often found trapped in these sedimentary rocks. They help in determining the flora and fauna of the earth’s past. This discipline of science that studies fossils are known as Palaeontology.