The correct answer "All of the Above".
Charlemagne, who at the time was King of the Franks and Lombards, was crowned as the First Holy Roman Emperor in the year 800 AD by Pope Leo III on Saint Peter's Basilica on December 25th. All of the following rulers who succeeded him considered themselves as descendants of Charlemagne's empire.
Under his rule, he united much of western Europe under the Christian Faith. This was considered a time of great cultural and intellectual development in the Empire.