Why did vassals have to serve lords?

Because the lords gave them their land in return if someone attack the land the vassals would protect it they got land for protecting and then if they got a big enough land they could sell some and become lords and then they would have vassals so you could get land and then sell some of it and you would get vassals

Explanation: I have taken the test before and I know because I like this kind of stuff. :)

affirmative action refers to the policies that take gender, race, or ethnicity into account in order to promote equal opportunity.

employers subject to title vii are prohibited from taking race or sex into account in any employment decisions. aa is a penalty for having any job group substantially statistically "underutilized" in any race or either sex. the employer must take steps to eliminate the underutilization, then stop, ending its aa efforts

is this question from a book? ?