what factor contributed to the development of japan's feudal system?
a. the central government became weak and lost power.
b. china’s han dynasty took control and formed the new structure.
c. an increase in trade led to a need for a new system.
d. the mongol invasion established a new government that created the system.

The central government became weak and lost power.

Explanation:

The Kamakura period started around 1185 A.D. When after a period of conflict Minamoto no Yoritomo consolidated his power over Japan. However, he was not an emperor but a warlord.  The emperor gave him the title of Shogun. The legitimacy of the Shogun was based solely on strength.  

Yoritomo decentralized power and stablished regional governments ruled by powerful families who geared and financed their own armies.  

The central power of the emperor was empty now, and other warlords would constantly challenge the shogun.  

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