The question is "How many..." This means the answer will be a number. So it boils down to what number has the same number of letters as the number it means. The only number in English that satisfies that condition is four. In, e.g., German the answer could be vier or, if you spell it with a ue rather than ü, fuenf would also work, so there wouldn't be a unique answer in German. Dunno about Nederlands.