The correct answer is "Population declined in urban areas".
During this period of time, between 100 CE and 1000 CE, Europe was governed under the concept of "Manorialism", which was a principle of rural economy that originated during the Roman Empire. Manorialism was based on the vesting of legal and economic power from the nobility to a "Manor", who controlled a certain extension of land and had to power to manage it and gain the most profit out of it. he would achieve this with the use of peasants, who worked the land.