Final answer:
A vassal is expected to show loyalty to a lord by providing military service.
Step-by-step explanation:
In feudal societies, a vassal is expected to show loyalty to a lord by providing military service. This means that the vassal is obligated to fight for the lord in times of conflict and assist in the lord's military endeavors. This military service could involve serving as a knight or providing soldiers and resources when required.
Learn more about Loyalty of vassals to lords