The political order under feudalism was dependent upon the relationship between lords and their vassals. the responsibility of the vassal included a. an oath of loyalty and a pledge of military service. b. the payment of taxes to the king or queen of the country. c. the promise to spread the christian faith to their lands. d. an agreement to keep the lower classes under control.

The correct answer is option A. "an oath of loyalty and a pledge of military service".

Explanation:

The feudal system that prevailed during medieval Europe functioned by lords who owned pieces of land and vassals that served the lords. The responsibility of the vassal included an oath of loyalty and a pledge of military service to the lords. The oath was known as oath of fealty, from the Latin fidelitas (faithfulness), and obligated the vassal to always remain faithful to the lord.

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