What was the relationship between the king and warlords?

In return of the land the lords got from their king, they were given certain responsibilities and roles in order for the feudal system to work out: They had to serve the royal council. They had to provide the King with knights to defeat any kind of war. They had to provide food and other necessities to the king.

Explanation:

answer; i believe that the correct answer is ; unified

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."