Final answer:
Genghis Khan's greatest achievement was the formation of a powerful Mongol Empire, which became the largest continuous empire in history with a sophisticated military and legal code.
Therefore, option C is correct.
Step-by-step explanation:
One of Genghis Khan's greatest achievements was the formation of a powerful Mongol Empire. His effective military strategies and mighty war machine allowed him to conquer vast territories, creating the largest contiguous empire in history. Genghis Khan also established a legal code, known as the yassa, which aimed to unify his diverse empire under a common framework. Moreover, his grandson, Kublai Khan, expanded the empire further and had a significant role in promoting trade along the Silk Road.He united a million or so of the world's people and created the world's largest empire through conquests that spanned from China to Syria and Russia to Korea. This empire lasted for nearly two centuries and brought about significant changes in the regions it ruled.