The correct answer is option 'A': Catenation.

Catenation is the property of self-linkage among identical atoms to form long-chain compounds. It is a unique property of carbon atoms, which can form covalent bonds with other carbon atoms, forming long chains or rings. This ability of carbon to form strong bonds with itself is the basis of organic chemistry.

Carbon has four valence electrons, allowing it to form up to four covalent bonds with other atoms. When carbon atoms bond with each other, they can form long chains, branched chains, or ring structures. This ability to form a diverse range of structures is what gives rise to the vast complexity and diversity of organic compounds.

Catenation is not limited to carbon; other elements like silicon, sulfur, and phosphorus also exhibit this property to some extent, but carbon is the most prominent element known for catenation.

Catenation is responsible for the formation of various organic compounds, including hydrocarbons, alcohols, carboxylic acids, and many more. For example, in hydrocarbons, carbon atoms can form single, double, or triple bonds with each other, giving rise to different types of hydrocarbons such as alkanes, alkenes, and alkynes.

Catenation also allows for the formation of isomers, which are compounds with the same molecular formula but different structural arrangements. Isomerisation, mentioned as option 'B', is a different concept that involves the rearrangement of atoms within a molecule to form isomers.

Superposition, mentioned as option 'C', is not related to the property of self-linkage among identical atoms, but rather refers to the combining or overlapping of waves.

Halogenation, mentioned as option 'D', refers to the process of adding halogen atoms (such as chlorine or bromine) to a molecule, and is not directly related to the property of self-linkage among identical atoms.

In conclusion, the property of self-linkage among identical atoms to form long-chain compounds is known as catenation, which is a unique property of carbon atoms. Catenation is responsible for the vast diversity and complexity of organic compounds.