Molecules that join side by side as well as end to end are described as

• A. Bond
• B. Cross-linked
• C. Butyl Rubber
• D. Ceramic coating/ frit

Answer: (B)

Cross-linking describes polymers where chains are connected at multiple points, both along the chain and between chains, forming a three-dimensional network. This combination of end-to-end and side-to-side connections locks the structure in place, making the material more rigid, less soluble, and able to withstand higher temperatures compared to linear polymers. That is why molecules joining both along their length and between different chains best matches cross-linked. A simple bond wouldn’t create a network, butyl rubber is a polymer whose properties arise from cross-links rather than just the bonding description, and a ceramic coating/frit is not about polymer connectivity.