The unique ability of carbon to form strong covalent bonds with other carbon atoms, building large molecules, is called:

1. Carbon-carbon covalent bonds are strong and stable. 2. This lets carbon atoms link into long chains and rings, forming very big molecules. 3. This property of self-linking is named catenation. 4. Rule out D: isomerism is having the same molecular formula but different structures, a different cause of variety. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 9 "Carbon Compounds", p.122_