The correct answer is option 4: None. This means that all of the options mentioned in the question are included in the National Air Quality Index. Let`s look at each option to understand why:

Option 1: Sulphur - Sulphur dioxide (SO2) is a common air pollutant that is included in the National Air Quality Index. It is produced by burning fossil fuels, particularly coal and oil.

Option 2: Nitrogen dioxide - Nitrogen dioxide (NO2) is another common air pollutant that is included in the National Air Quality Index. It is produced by burning fossil fuels, vehicle emissions, and industrial processes.

Option 3: Lead - Lead (Pb) is also a pollutant that is included in the National Air Quality Index. However, it is now less prevalent as an air pollutant due to the phasing out of leaded gasoline and the regulation of lead emissions from other sources.

So, it is clear that all of the options mentioned, including sulphur, nitrogen dioxide, and lead, are included in the National Air Quality Index. Therefore, option 4, which states "None," is not the correct answer.

Alert - correct answer should be: There is an error in the question. All of the options