What did a vassal promise to an overlord in exhange for land?​

A vassal gave the lord military support and protection...In turn the lord gave a vassal fiefs.  . (land)

Explanation:

A lord was in broad terms a noble who held land, a vassal was a person who was granted possession of the land by the lord, and a fief was what the land was known as. In exchange for the use of the fief and the protection of the lord, the vassal would provide some sort of service to the lord.

c

explanation:

a social contract.

"a social contract is an agreement between citizens and their leader where the citizens give up certain freedoms in exchange for protection. the constitution of the united states is an example of a social contract."