In the cities of our country, which among the following atmospheric gases are normally considered in calculating the value of Air Quality Index?1.Carbon dioxide2.Carbon monoxide3.Nitrogen dioxide4.Sulfur dioxide5.MethaneSelect the correct answer using the code given below

1. A

   1, 2 and 3 only

   Carbon dioxide is a greenhouse gas but is not among the pollutants used in India’s National Air Quality Index. Pairing CO2 with CO and NO2 therefore fails. 1, 2 and 3 only is not the key.

2. B

   2, 3 and 4 only

   India’s AQI (NAQI) is computed from a set that includes carbon monoxide, nitrogen dioxide and sulfur dioxide (along with PM10, PM2.5, ozone, ammonia and lead). Carbon dioxide and methane are not in that AQI basket. Statements 2, 3 and 4 only are correct, so (b) is the official key.

3. C

   1, 4 and 5 only

   Carbon dioxide, SO2 and methane mixes a greenhouse-gas pair with one true AQI gas and omits CO and NO2. 1, 4 and 5 only is wrong.

4. D

   1, 2, 3, 4 and 5

   All five would include CO2 and methane, which AQI does not use. This option is not the key.

Summary. Official key is (b) 2, 3 and 4 only. The Central Pollution Control Board’s National AQI (2014) uses eight pollutants: PM10, PM2.5, NO2, SO2, CO, O3, NH3 and Pb. CO2 and methane matter for climate, not for the daily urban AQI colour scale. Candidates should not dump every carbon-containing gas into AQI. Only CO, NO2 and SO2 among the five listed gases count.