On our CodyCross answers based website we have the solution for A gas that makes up 75% of the Earth's atmosphere. CodyCross game includes different missions and events which update daily so you can earn tokens that are mostly needed to help with answers for challenging clues. Now let's focus on the answer you need for A gas that makes up 75% of the Earth's atmosphere by scrolling down which is part of CodyCross Children's Books Group Puzzle 15.