Are you absolutely sure this is accurate? For example, by most measures, Mexico City is 1.5x the size of Moscow, and Pyongyang is nowhere near larger than Paris
According to Wikipedia, Moscow has roughly 2.5 million more people living there than Mexico City. Pyongyang has about a million more than Paris. You could be right, but this quiz is solely based off of what I found on Wikipedia. Link - http://en.wikipedia.org/wiki/List_of_national_capitals_by_population