The correct option is C PV=RT+Pb
The van der Waals equation is given by
For one mole of a real gas, this can be reduced to
At relatively high pressure, the volume of the gas is very small.
Hence, we cannot neglect the term nb but we can neglect the term (aV2) as it is negligible when compared with the value of P.
Thus, option (c) is the correct answer.