Which of the following is a cross-linked polymer?A: TeflonB: OrlonC: NylonD: Bakelite

The correct answer is D: Bakelite.

Bakelite is a cross-linked polymer and is the only option among the choices provided that fits this category. Bakelite is a thermosetting plastic that was one of the first synthetic plastics to be widely used. It is formed by the cross-linking of phenol and formaldehyde under high heat and pressure. The cross-linking process creates a three-dimensional network of polymer chains, resulting in a rigid and durable material.

Teflon (option A) is not a cross-linked polymer but a type of polytetrafluoroethylene (PTFE), which consists of long chains of repeating units without cross-links. Orlon (option B) and nylon (option C) are both examples of linear polymers, meaning their polymer chains are not cross-linked.