UPSC Civil Services 2019 Prelims General Studies Paper I

- As per google scholar research papers, Biomass burning is a source of greenhouse gases, carbon dioxide, methane, and nitrous oxide. In addition, biomass burning is a source of chemically active gases, including carbon monoxide, non-methane hydrocarbons, and nitric oxide. These gases, along with methane, lead to the chemical production of tropospheric ozone. So, answer should be D: 1, 2,3 and 4.