The nobles: practiced plowing

protected the serfs from attack

jousted

brought unity to medieval society

Although they did bring some degree of stability, their main job was to protect the serfs.

The correct answer is B. Protected the serfs from attack

Explanation:

During the Middle Ages, the nobles were one of the higher social classes in medieval society just below the king. Nobles had an important role because they were in charge of lands provided by the king, due to this, it was a duty of the nobles to provide military protection and support to the king, usually through knights. Besides this, nobles were in charge of giving peasants or fiefs land and protecting them if necessary in the case of an attack or similar situation, while peasants plowed and farmed the land provided by the nobles. Thus, it can be concluded the nobles protected the serfs from attack.