18. The relation PV = nRT holds for all ideal gases. The additional relation PVy holds for an adiabatic process. The figure below shows two curves: one is an adiabat and one is an isotherm. Each starts at the same pressure and volume. Which statement is correct? (Note: "of" means "is proportional to".) a. P oc 1 P oc Isotherm: ; Adiabat: V : A is both an isotherm and an adiabat. b. P oc Poc Isotherm: ; Adiabat: : B is an isotherm, A is an adiabat. C. Poc P oc Isotherm: ; Adiabat: : A is an isotherm, B is an adiabat. d. P oc Poc Isotherm: ; Adiabat: : B is both an isotherm and an adiabat. e. cannot answer without additional information about the starting temperature