Read the following passage and give the answer:

Delhi tried very hard, but it was not enough. In the run-up to D-Day, the sound of firecrackers had not been heard. The Supreme Court’s ban on its sale had made it difficult to acquire, but many people, including schoolchildren, had decided to break tradition for clean air. And until 7 pm on Diwali, most neighbourhoods were quiet. Around that time the first sound of firecrackers exploding was heard, slowly building to a crescendo. But it was nowhere near the blitzkrieg of the past, not even half of it. And long before midnight, it was all over.

The bad news broke at dawn. It was a visibly smoggy morning. Air pollution levels peaked on Diwali night and remained dangerously high through Friday afternoon, as reflected in real-time monitoring data from the Central Pollution Control Board (CPCB) and the Delhi Pollution Control Committee (DPCC).

The CPCB, however, pointed to a silver lining. He said this year’s Air Quality Index (AQI) was better than Diwali’s in the past two years despite the harsh weather conditions. At Diwali last year (October 30, 2016), the city’s average AQI was in the “serious” category at 426, while the year before (November 11, 2015), it had been in the “very poor” category. ” at 327. This time, it was marginally lower at 326.

There are so many factors that affect air quality, from wind speed and direction to crop stubble burning in neighbouring states, that it’s hard to definitively identify the main culprit. What must be recognized, however, is that at least most people are willing to stick with what may seem like unpleasant decisions for a better quality of life.

However, the data is troubling informed observers, particularly the massive spikes in levels of PM 2.5 (respirable fine particulate matter pollutants) and PM 10 (coarse particulate matter pollutants) on Thursday night after 10 p.m. p.m. Delhi peaked at 656 micrograms per cubic meter around midnight.

However, the data also shows that despite unfavourable weather conditions, the air quality at Diwali this year was better than last year. It hadn’t been as good in the two days before Diwali due to the intrusion of humid air from the southeast, coupled with prevailing calm wind conditions. The average mixing height (the height at which smoke or air rises, mixes and disperses) recorded on October 18 and 19 was 547 meters and 481 meters, respectively, according to the CPCB. It must be at least 1000 meters for a correct dispersion.

Q:

The AQI levels after Diwali this year were

• 1
  the same as in other years.
• 2
  higher than other years.
• 3
  lower than other years.
• 4
  could not be ascertained.