D) Revival of the ideal of a unified Christian community
Explanation:
The crowning of Charlemagne by Pope Leo III was significant in a number of ways. For Charlemagne, it was necessary because it encouraged to give him higher reliability. It gave him the rank of a dictator, giving him the only ruler in Europe west of the Byzantine emperor in Constantinople. He was the first known monarch to rule from western Europe since the downfall of the Western Roman Empire three ages old. He attained the height of his power in 800 when he was honored Emperor of the Romans by Pope Leo III on Christmas Day at Rome's Old St. Peter's Basilica.
