Natural rubber is cis -1,4- polyisoprene. It has long flexible chains, weak intermolecular forces, and exhibits elastic properties.Natural rubber contains C and H atoms only. Thus, it has non-polar C-H bonds and weak van der Waals forces of attraction. On the other hand, cellulose, polyvinyl chloride (PVC) and nylon contains \ ext{C, H} and heteroatoms (\ ext {Cl, N or O}) . Thus, they have polar bonds and dipole interactions. Among cellulose, polyvinyl chloride (PVC) , nylon and natural rubber, the polymer in which intermolecular forces of attraction are weakest is natural rubber. Hence, option C is correct.