Statement (a) is correct; AQI provides a daily update on air quality. Statement (b) is correct; the AQI scale is designed such that a higher value indicates a greater level of air pollution and poorer air quality. Statement (c) is correct; the Indian AQI is calculated on a scale ranging from 0 to 500, divided into six categories. Statement (d) is correct; AQI is calculated based on the measured concentrations of eight major pollutants (PM2.5, PM10, SO2, NO2, CO, O3, NH3, and Lead) at monitoring stations.