The correct option is B RT
If the graph is plotted for 1 mole gas in such a way that PV is plotted against P, then intercept of the graph for real gas will be RT.
For 1 mole of real gas, the van der waals equation is (P+aV2m)(Vm−b)=RT
PVm−Pb+aVm−aV2m=RT
PVm=RT+Pb−aVm+abV2m
To calculate the intercept, P→0, so Vm→∞.
The last two terms on the right side of the equation can be neglected.
PVm=RT+Pb
Thus, when P=0, intercept =RT