The correct option is A constants a and b are negligibly small
According to van der Waal's equation (P+aV2)(V−b)=RT for one mole of the gas. Obviously if a and b are small, aV2 and b can be neglected as compared to P and V and the equation reduces to PV=RT for one mole of gas.
∴ A real gas will resemble an ideal gas when constant a and b are small