The correct option is C cation polymerisation polymer
ELASTOMER - Elastomers are rubber-like solids with elastic properties.
FIBRE - Fibre polymers are the thread forming solids with high tensile strength and high modulus.
THERMOSETTING POLYMER - These polymers are cross-linked or heavily branched molecules, which on heating undergo extensive cross-linking in moulds and again become infusible.
POLYSTYRENE - Polystyrene is a thermoplastic polymer. It is formed by cation polymerisation. Hence, it is an example of a cation polymerisation polymer.