Answer: a. The rulers of the Yuan dynasty adopting Chinese court culture and methods of rule
Explanation:
The Mongol conqueror Genghis Khan united the nomadic Mongol clans and established a vast Mongol empire that controlled a significant part of the world in its time with part of those dominions being China.
When he died, his son took over and then his grandson Kublai Khan took over and established the Yuan dynasty in 1271. After this, Kublai employed the methods of Chinese rule that he had found amongst the Chinese thereby assimilating the conquering Mongols into Chinese lifestyle.
I've seen this question before -- I'm guessing you're working with a chapter on European Renaissance and Reformation that featured a secondary source (source B) reference from historian Steve Ozment. In document A, from a letter to the pope sent by Martin Luther, Luther accused the Roman Catholic Church of having become a den of thieves, that the whole hierarchy needed reform. That early letter (from 1520) supports Ozment's claim that Luther's Reformation movement began as a protest against "arbitrary, self-aggrandizing hierarchical authority" in the church.
Answer: C is the correct answer.
Explanation: The Underground Railroad was a fascinating series of homes and businesses that risked their freedom or sometimes their lives to help slaves reach freedom. They would hide and feed escaped slaves and give them directions to the next "stop" on the route.