Answer : 4. "All the above"
Explanation :

Answer: D) All the above Explanation: A greenhouse gas (GHG) is any gas in the atmosphere that absorbs and emits radiation in the thermal infrared range.   The increase in average global temperatures that results from an enhanced greenhouse effect. Effects of increased greenhouse gas emissions: Increases in the different greenhouse gases have other effects apart from global warming including ocean acidification, smog pollution, ozone depletion as well as changes to plant growth and nutrition levels.