Which statement best explains how Charlemagne affected European feudalism? OA. He strengthened it by sending his knights to serve in the army of the Byzantine Empire to gain military experience. B. He strengthened it by expanding the practice of giving land to nobles in exchange for loyalty and military service. C. He weakened it by encouraging his nobles to sell much of their land to the recently arrived Vikings and Magyars. OD. He weakened it by upholding the legal rights of peasants against wealthy landowners who sought to enslave them.