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.

1. Oxides of sulphur — Steel plants emit SOx mainly from burning coal/coke and use of sulphur-bearing raw materials. Correct.

2. Oxides of nitrogen — High-temperature combustion in coke ovens, sinter plants and blast furnaces releases NOx. Correct.

3. Carbon monoxide — Incomplete combustion and blast furnace/coke oven gases contain significant CO. Correct.

4. Carbon dioxide — Iron and steel production is a major source of CO2 due to coke use and reduction of iron ore. Correct.

Since all four are important pollutants released by the steel industry, the correct answer is (d) 1, 2, 3 and 4.