You may want to reference (Pages 532 - 538) Section 13.1 while completing this problem.
Which two statements about gas mixtures are true?
(a) Gases always mix with other gases because the gas particles are too far apart to feel significant intermolecular attractions or repulsions.
(b) Just like water and oil don’t mix in the liquid phase, two gases can be immiscible and not mix in the gas phase.
(c) If you cool a gaseous mixture, you will liquefy all the gases at the same temperature.
(d) Gases mix in all proportions in part because the entropy of the system increases upon doing so.