The reason is considered a success for Genghis Khan in his invasion of China is that he invaded and conquered South China.
Option D is the correct answer.
Genghis Khan was the king of the Mongol empire. After his demise, the empire became vicinal in ancient times.
Genghis Khan was known to be the most popular ruler in the ancient era due to his military successes. He acquired the Southern part of China in the year 1279 after defeating the Yuan dynasty.
Therefore, the conquering of South China by Genghis Khan is one of the reasons for the invasion of China.
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