Verified answer

This may be an attempt to create a "trick" question. Fact is, the N2 will occupy 100% of the room, the O2 will occupy 100% of the room, regardless of the presence of the other or not. The question "tricks" you into imagining the room (i.e. 10 feet high) having only 8 feet of Nitrogen and 2 feet of Oxygen, while this is obviously not true..

Any gas will fill the room, and using the data above you could correctly state that "80% of the gas molecules present in the room would be Nitrogen" but not that only 80% of the room would have Nitrogen in it.

Hope this helps.