Monaco is a city state where Monaco is the capital, there is no distinction between the city and state. Monte Carlo is the largest of the four quartiers. Answer is ambiguous, ill add an explanation to the quiz to make it more clear. As for Nauru, it does not have an official capital, Yaren district is however the de facto capital. I can add it to the quiz with an explanation
Sudan and Taiwan should not be on here (which cities are you saying are larger than Khartoum and Taipei respectively?), and are both out of order alphabetically.