The correct match between item-I and item-II is:
Item-I                       Item-II
(a) Natural rubber    (I) 1,3-butadiene + styrene
(b) Neoprene           (II) 1,3-butadiene
(c) Buna-N              (III) chloroprene
(d) Buna-S              (IV) Isoprene

We first recall the standard IUPAC names of the monomeric units that build the well-known elastomers mentioned in Item-I.

Natural rubber is scientifically described as $$\text{cis-1,4-polyisoprene}$$. Hence its repeating unit is derived from the monomer $$\text{isoprene}$$ $$\bigl(2\text{-methyl-}1,3\text{-butadiene}\bigr).$$ We therefore connect “Natural rubber” with “Isoprene”.

Neoprene is produced by the free-radical polymerisation of $$\text{chloroprene}$$ $$\bigl(2\text{-chloro-}1,3\text{-butadiene}\bigr).$$ Thus “Neoprene” must be paired with “Chloroprene”.

Buna-S is a copolymer obtained from $$1,3\text{-butadiene}$$ and $$\text{styrene}$$. Accordingly, the correct description for Buna-S is “1,3-butadiene + styrene”.

Buna-N (the “N” stands for “nitrile”) is produced from $$1,3\text{-butadiene}$$ together with $$\text{acrylonitrile}$$. Because acrylonitrile does not appear in Item-II, the closest remaining entry is the simple monomer $$1,3\text{-butadiene}$$ itself. Hence we associate Buna-N with “1,3-butadiene”.

Collecting these matches we have

$$\begin{aligned} \text{(a) Natural rubber} &\longrightarrow \text{(IV) Isoprene} \\ \text{(b) Neoprene} &\longrightarrow \text{(III) Chloroprene} \\ \text{(c) Buna-N} &\longrightarrow \text{(II) 1,3-butadiene} \\ \text{(d) Buna-S} &\longrightarrow \text{(I) 1,3-butadiene + styrene} \end{aligned}$$

On comparing this sequence with the given options, we observe that Option C lists exactly these pairings.

Hence, the correct answer is Option C.