Which one of the following cities became the mega city by 1850 ?

Paris

London reached the million mark in 1800, followed by Paris in 1850, New York in 1860, and by 1950 there were around 80 such cities. There were 162 million cities in mid 70’s and there was threefold increase in 2005 and the number reached to 438. In 2016, there were 512 cities with at least 1 million inhabitants globally. By 2030, a projected 662 cities will have at least 1 million residents.