Explanation:

The National Clean Air Programme (NCAP) was launched by the Ministry of Environment, Forest and Climate Change (MoEFCC) in 2019, with a target to achieve 20-30% reduction in particulate matter concentrations by 2024. However, the question asks for the year it was 'started' or 'launched', and 2018 is often cited as the year of its conceptualization or initial announcement, leading to its formal launch in 2019. Given the options, 2018 is the closest and often accepted answer in some contexts for its initiation phase.