Charlemagne significantly changed the Holy Roman Empire by expanding its size through military conquests. His rule united much of Western Europe and contributed to the spread of Christianity and culture. This expansion laid the groundwork for the future of Europe. ;
Charlemagne changed the Holy Roman Empire mainly by expanding its size through military conquests. His efforts united much of Western Europe and laid the foundations for the future of the region. Therefore, the correct answer to the student’s question is A. He expanded its size.
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