European countries each have their own ways of making and enforcing their citizenship laws. It is usual to discuss the concept of citizenship before and after the Second World War, which changed the concept of citizenship dramatically. Citizenship was a contract between the rights-holder, or citizen, and the nation-state. This was actually an exclusionary contract because migrants from other nations did not have any chance to become citizens. This style was dominant in nation-states until the mid-20th century, but started to decline in popularity as a result of the huge migrations after World War II. The correct answer is E.