The correct answer is A. GHGs.
GHGs, or greenhouse gases, are gases that trap heat in the atmosphere. This trapped heat causes the Earth’s temperature to rise. The main GHGs are carbon dioxide, methane, nitrous oxide, and ozone.
CFCs, or chlorofluorocarbons, are chemicals that were once used in refrigerators and air conditioners. CFCs are very effective at trapping heat in the atmosphere, and they are a major cause of ozone depletion.
CH4, or methane, is a gas that is released from natural sources, such as wetlands, and from human activities, such as agriculture and waste management. Methane is a more potent greenhouse gas than carbon dioxide.
NO2, or nitrogen dioxide, is a gas that is released from fossil fuel combustion and from industrial processes. NO2 is a major contributor to acid rain.
All of these gases contribute to global warming, but GHGs are the main cause.