On last question, could use help Which of the following is true for a gas under conditions of very high pressure?

PV > nRT, because the real volume of the gas would be more than the ideal volume.
PV = nRT, because intermolecular forces are considerable at very high pressures.
PV = nRT, because all gases behave as ideal gases at very high pressures.
PV < nRT, because the volume of the gas would become negligible.