Explanation:

Limestone is a sedimentary rock that is primarily composed of calcium carbonate (CaCO3) in the form of mineral calcite. It is formed from the accumulation of organic and inorganic materials, such as marine organisms, shells, and sediment, over millions of years.

However, limestone is not a metamorphic rock, which is a type of rock that has undergone significant changes in temperature and pressure due to geological processes such as tectonic activity or magma intrusion. Metamorphic rocks are formed from pre-existing rocks that have been transformed or altered by heat and pressure, resulting in changes in their mineral composition, texture, and structure.

Therefore, the correct answer to the question is option 'D', which states that limestone is not a metamorphic rock. It is a sedimentary rock that is formed through the accumulation of organic and inorganic materials over time.

Conclusion:

In summary, limestone is a sedimentary rock that is primarily composed of calcium carbonate and is formed through the accumulation of organic and inorganic materials over millions of years. It is not a metamorphic rock, which is a type of rock that has undergone significant changes in temperature and pressure due to geological processes.

Rocks are classified on the basis of their geological formation, physical characteristics and chemical composition. If we classify lime stone, on the basis of its geological formation it is a sedimentary rock (sedimentary rocks are rocks which are formed by deposition of produces of weathering on pre-existing rocks), sedimentary rocks are also called as aqueous rocks or stratified rock. *Where as if we talk about metamorphic rocks these rocks are formed by change in characteristics of pre-existing rock when subjected to great heat and pressure.*