Answer:
Charlemagne, is the right answer.
Explanation:
Charlemagne, the Frankish monarch was crowned by Pope Leo III on the sovereignty of the Holy Roman Empire. In his inadequacy to defend his territory from foreign invasions, Pope Leo III requested to Charlemagne to protect his people from such intrusions. Accordingly when Charlemagne assisted to Pope to protect his people, Pope Leo III in the year 800 CE crowned him as the "Emperor of the Romans".
