Of the gases listed below, which is NOT believed to be responsible for enhancing the earth's greenhouse effect?

Of the gases listed below, which is NOT believed to be responsible for

1.	Of the gases listed below, which is NOT believed to be responsible for enhancing the earth's greenhouse effect?
A.	Chlorofluorocarbons (CFCs)
B.	Molecular oxygen (O2)
C.	Nitrous oxide (N2O)
D.	Carbon dioxide (CO2)
E.	Methane (CH4)
Answer» C. Nitrous oxide (N2O)