Read the following text carefully : According to the 2021 World Air Quality Report, India is home to 63 of the 100 most polluted cities. The study also found that PM 2.5 concentration (tiny particles in the air that are 2.5 micrometres or smaller in length) in 48% of the country's cities are more than 10 times higher than the WHO's air quality guidelines level. Undoubtedly, this has made air pollution as one of the most pressing environmental issues in India. Vehicular emission, industrial waste, cooking smoke, the construction sector, crop burning and power generation are among the biggest sources of air pollution in India. The country's dependence on coal, oil and gas due to rampant electrification makes it the world's the largest polluter, contributing over 2.65 billion metric tonnes of carbon to the atmosphere every year. In 2021, India was among the world's most polluted countries, second only to Bangladesh. The annual average PM 2.5 level in India was about 58.1 ug/m^3 in 2021. Scientists have linked persistent exposure to PM 2.5 to many long-term health issues including heart and lung disease, as well as 7.5 million premature deaths each year. On the basis of the above passage and common understanding, answer the following questions : (i) State and discuss the functions of Central Pollution Control Board (CPCB), set up by the Government of India. (ii) State any four sources of air pollution in India.