Elastomers: choose the statement that best characterises elastomeric materials in general industrial practice.

Introduction / Context:
Elastomers are polymers that undergo large reversible deformations. Understanding their crosslinking state and mechanical profile is important for designing seals, tyres, and vibration isolators. Most industrial rubbers are cured (vulcanised), creating a network that provides elastic recovery without flow.

Given Data / Assumptions:

• Industrial elastomers are lightly crosslinked via vulcanisation or peroxide cure.
• Crosslinking renders them thermoset in service (no melting on reheating).
• Neat elastomers are not known for high flexural strength or extreme tensile strength without reinforcement.

Concept / Approach:
Elasticity requires network junctions that restore the original shape after strain. This is achieved by a sparse crosslinked network, i.e., a thermoset. Fillers (carbon black, silica) and fibers improve tensile and tear properties, but the base elastomer alone does not rival high-temperature engineering thermoplastics in tensile or heat resistance.

Step-by-Step Solution:
Identify the defining feature: lightly crosslinked networks → thermosetting.Eliminate protein derivatives (not representative of synthetic elastomers).Eliminate claims of inherently high flexural or tensile/heat strength without context.

Verification / Alternative check:
Rubber technology texts describe vulcanisation and the transition from viscous gum to elastic network as the hallmark of elastomers.

Why Other Options Are Wrong:
(b) Not a defining class; (c) and (d) exaggerate properties absent reinforcement.

Common Pitfalls:
Confusing thermoplastic elastomers (TPEs) with conventional vulcanised rubbers; TPEs have physical crosslinks but still behave like thermoplastics in processing.

Final Answer:
They are typically thermosetting materials (lightly crosslinked for elastic recovery).