Which of the following are some important pollutants released by steel industry in India? 1. Oxides of sulphur 2. Oxides of nitrogen 3. Carbon monoxide 4. Carbon dioxide Select the correct answer using the code given below.

The steel industry involves high-temperature processes, primarily the combustion of coal/coke and the smelting of iron ore. These processes release several atmospheric pollutants. 1. Oxides of sulphur (SOx): Coal and iron ore often contain sulphur, which gets oxidized and released as SO2 during combustion and smelting. 2. Oxides of nitrogen (NOx): High temperatures in furnaces cause atmospheric nitrogen and oxygen to react, forming NOx. 3. Carbon monoxide (CO): Incomplete combustion of carbon-based fuels (like coke in blast furnaces) leads to the release of CO, a toxic gas. 4. Carbon dioxide (CO2): Complete combustion of carbon fuels and the chemical reduction of iron ore using carbon (coke) are major sources of CO2 emissions, a significant greenhouse gas. Therefore, all four listed substances (1, 2, 3, and 4) are important pollutants released by the steel industry in India.