Consider the following statements. (i) Polystyrene is a homopolymer whereas buna-N is a copolymer. (ii) Condensation polymers can be obtained by condensation between two similar bi-functional monomeric units. (iii) Elastomers are the polymers in which the polymeric chains are held together by the weakest intermolecular forces. (iv) Buna-S and buna- N consist of close packing of chains which impart them crystalline nature. Which of the following is the correct code for the statements above?