The correct answer is A.
The Ruhr Valley in western Germany is the largest metropolitan region in Germany with over 10 million inhabitants. It has a population of over 5 million and it is the largest urban area in Germany and the third-largest in the European Union. The population density is 2,800 persons per square kilometer. Nationally, the population density in Germany is 230 persons per square kilometer. Therefore, the Ruhr Valley is the most densely populated area in the country.
The Ruhr Valley is located in the state North-Rhine Westphalia. The state has a population of 17,6 million and it is the most populous state in Germany. It features four of Germany's ten largest cities : Dusseldorf, Cologne, Dortmund and Essen. It is one of the most industrialized areas of the country.
