http://swissbaync5d7ykaz7dh7v4qjrb4gmen5aj3bogxrcgbb43ij34bjuyd.onion/pdf/Books/Survival/Medicine/quiz.htm
The gas composition of ordinary air is: a) 15% oxygen, 20% nitrogen, 5% other b) 20% oxygen, 75% nitrogen, 5% other c) 21% oxygen, 78% nitrogen, 1% other d) 24% oxygen, 79% nitrogen, 3% other e) 26% oxygen, 81% nitrogen, 3% other 2.