Which of the following is incorrect regarding 'AQI displayed by IQAir'?
1
It measures air quality levels of 100 major cities based on the concentration of lung-damaging airborne particles known as PM2.5.
2
The AQI displayed by IQAir is based on the US legend of the air pollution yardstick.
3
The rankings were segmented into 6 groups.
4
None of the above