Correct Answer - Option 1 : The highest demand for air purifiers is from Delhi and its nearby states.
Option 1 is the correct answer. It can be concluded from the given premise that the increase in the level of pollution in the city makes the people aware to buy something which can dampen its effect so people are buying air purifiers. Also, air pollution in Delhi or any city will naturally have some impact on its neighbouring areas.
Option 2 is invalid as the passage does not compare the quality of indoor and outdoor air.
Option 3 is eliminated because no opinion of the government is mentioned in the above passage.
Option 4 is eliminated because the number or percentage of sales of air purifiers is not mentioned in the passage.
Hence, Option 1 is the correct answer.