A、It can go deep to the lung and cause health problems. B、The public do not care about its existence. C、The problem has not yet

Smog-choked residents of New Delhi welcomed the New Year on Friday by new driving restrictions designed to pull millions of cars off the roads and improve air quality. The temporary measures allow private vehicles to operate in turn until January 15. Last year, the World Health Organization released data on air quality levels in 1,600 cities around the world, and Delhi was found to have the highest concentration of particulate matter smaller than 2.5 micrometers, also called PM2.5.
    PM2.5 particles are exceedingly small, but go deep into the lungs and cause health problems.
Scientists say coal-fired power plants, vehicles, construction dust, crop burning and cooking fuel use all contribute to high pollution levels in Delhi. Among these, the sharp rise in the use of private cars stands out. There are nearly 9 million registered vehicles in Delhi, The problem has attracted attention from top policymakers.
    The Supreme Court of India, which has been the most aggressive government bodies on pollution issues, has banned large SUVs in Delhi and raised taxes on commercial trucks entering the city. Expert said pulling cars off the road will raise public awareness over air pollution, and force the government to improve mass transit systems.
Question 5 to 7 are based on the news report you have just heard.
5. What change took place in New Delhi recently?
6. What helped bring about the change?
7. What do we learn about PM 2.5 from the news report?