The correct answer is:
According to the map, the borders of the Mongol Empire increased following the death of Genghis Khan. During his lifetime, Genghis Khan was able to capture parts of northern China and large areas in Central Asia. The greatest extent of the Mongol Empire occurred in 1279.
Genghis Khan was the founder and first Great Khan of the Mongol Empire. He rose to power by consolidating several of the nomadic tribes of Northeast Asia. After establishing the Empire and being declared Genghis Khan, he propelled the Mongol invasions that overcame most of Eurasia. By the end of his life, the Mongol Empire occupied a substantial portion of Central Asia and China, and after his death, the Mongol Empire became the largest contiguous empire in history.