Rubber il a natural rubber and it possesses elastic properties. It is also termed as elastomer and has a variety of uses. Natural rubber may be considered as a linear polymer of isoprene (Monomer) and is also called as cis - 1, 4 - poly isoprene.
Structure of isoprene (2 - methye - 1, 3 - butadiene) →

Structure of Natural rubber →

Molecule consist of various chains held by weak vanderwaal force of attraction.
so, the correct option is (A)