The correct answer is: a) Neighboring kingdoms.
Feudatory states were political entities that were subordinate to a larger kingdom or empire. They often paid tribute and provided military support to their overlords in exchange for protection and other benefits.
Option b) is incorrect because colonial powers were not typically the overlords of feudal states. In fact, colonial powers often sought to undermine and conquer feudal states in order to expand their own territory and influence.
Option c) is incorrect because religious institutions were not typically the overlords of feudal states. In fact, religious institutions often played a role in mediating disputes between feudal states and in providing spiritual guidance to their rulers.
Option d) is incorrect because merchant guilds were not typically the overlords of feudal states. In fact, merchant guilds often played a role in the economic development of feudal states, but they did not typically have political power.
In conclusion, the correct answer is: a) Neighboring kingdoms.