The right answer is "D) People wanted the protection that the nobles could provide them."
Basically, what happened in order for people to want the protection that the nobles could offer was that the economy suffered a contraction of commercial activities, the coins lost their circulation space and the agricultural production gained subsistence. In this period, the crisis of the Roman Empire favored a process of ruralization of the populations, who could no longer undertake commercial activities. This happened because of the constant wars promoted by the barbarian invasions and the crisis of the urban centers constituted during the height of the classic civilization
The ruralization of the economy also directly affected the social classes instituted in the interior of Rome. The formerly comprehensive class of slaves and commoners came to compose, with the Germanic peoples, a peasant class consolidated as the main labor force of the fiefs. Working in servitude, a peasant would be tied to rural life because of the threats of the conflicts of the High Middle Ages and the personal relationship established with the proprietary class represented there by the feudal lord.
The feudal lord represented the nobiliarchic land-holding class. Divided by different titles, the nobles could be responsible from the administration of a fief to the collection of fees or the military protection of a certain property.
