Classification of polymers based on molecular forces :-
(i) Elastomers having elastic character
(ii) Fibres are the polymers which have strong intermolecular forces between the chains(hydrogen bonds on dipole-dipole interaction)
(iii) Thermoplastics are the polymers which can be easily softened repeatedly when heated and hardened when cooled with little change in their properties.
(iv) Thermosetting are the polymers which undergo permanent change on heating.
Hence (c) is the correct answer.