Hello Dear the correct answer is B. i searched it on the web and this is the info i got :
History. Feudalism, in its various forms, usually emerged as a result of the decentralization of an empire: especially in the Carolingian Empire in 9th century AD, which lacked the bureaucratic infrastructure necessary to support cavalry without allocating land to these mounted troops.
Decentralization-the transfer of control of an activity or organization to several local offices or authorities rather than one single one.