Thermoplastic materials: which statement correctly describes them among the following choices?

Introduction / Context:
Thermoplastics are linear or lightly branched polymers that soften on heating and can be reshaped repeatedly within thermal limits. Recognising their behaviour distinguishes them from thermosetting resins, which form permanent crosslinked networks.

Given Data / Assumptions:

• Thermoplastics soften with heat and can be remoulded; they do not irreversibly cure like thermosets.
• Branching varies by polymer; some are linear (e.g., PET), some branched (e.g., LDPE), some are nearly linear (e.g., HDPE).
• Solubility is polymer–solvent specific; many thermoplastics are soluble in appropriate solvents.

Concept / Approach:
Examine each claim for absolute accuracy. “Do not soften” is false; thermoplastics do soften. “Always heavily branched” is false; topology varies. “Insoluble in all solvents” is false; many dissolve in suitable solvents. Hence the only correct choice from the provided options is “None of these.”

Step-by-Step Solution:
Evaluate thermoplastic behaviour on heating: softening/remelting is expected.Check molecular architecture: not universally heavily branched.Assess solubility: depends on polymer–solvent interactions; not universally insoluble.Conclude that none of the given statements is correct.

Verification / Alternative check:
Processing of thermoplastics by extrusion, injection moulding, and thermoforming inherently relies on softening/melting upon heating.

Why Other Options Are Wrong:
(a): Opposite of thermoplastic behaviour.(b): Architecture is polymer-specific.(c): Many thermoplastics are soluble (e.g., PS in aromatic solvents).(e): Describes thermosets, not thermoplastics.

Common Pitfalls:
Confusing solvent resistance of some engineering thermoplastics with universal insolubility.

Final Answer:
None of these.