The correct answer is B. They introduced Eastern culture and literature to Europeans.
While Genghis Khan and Kublai Khan did not have direct military campaigns in Europe that led to significant destruction as suggested by option D, their rule and the vast Mongol Empire facilitated trade and cultural exchange between the East and West. This contact introduced new ideas, technologies, and cultural elements to Europe. Options A and C are not accurate in the context of their direct impacts, as modern warfare concepts were not primarily influenced by the Mongols, and the spread of Christianity was not a focus of their leadership.