The Flory$-$Huggins interaction parameters listed below correspond to polystyrene in different solvents. Choose the best solvent for polystyrene.

a$.$ Cyclohexane: $=0\mathrm{.}510$

b$.2-$Butanone: $=0\mathrm{.}490$

c$.$ Benzene: $=0\mathrm{.}475$

d$.$ Ethylbenzene: $=0\mathrm{.}450$

e$.$ Cumene: $=0\mathrm{.}444$