Which of the following groups consists entirely of major greenhouse gases ?

Carbon dioxide (CO2), nitrous oxide (N2O), and chlorofluorocarbons (CFC) in "CO2, N2O, CFC" are all major greenhouse gases that absorb and re-emit thermal infrared radiation in the atmosphere. In the other groups, neon, argon, and krypton are noble gases transparent to infrared radiation, SO2, CO, and NO2 are primarily air pollutants rather than primary direct greenhouse gases, and in "Ethane, Methane, Butane" only methane is a major greenhouse gas while ethane and butane are short-lived alkane hydrocarbons.