Final answer:
The gas that does not fit the pattern is ozone (O3).
Step-by-step explanation:
The gas that does not fit the pattern is E. O3 (ozone). The other gases listed (A. CH4, B. CO2, C. N2, D. N2O) are all compounds made up of two or more different elements. O3, on the other hand, is a molecule made up of three oxygen atoms. It does not fit the pattern of the other gases.