Questions Refer to the Passage Below

Questions refer to the passage below.
"[Many] of our Fathers have gone into the countries of the Mongols, and Turks, and Chinese and have taught them the Gospel, and at the present time there are many Mongols who are Christians. For many of the sons of the Mongol kings and queens have been baptized and . . . they have established churches in their military camps . . . Now the king [of the Mongols] . . . hath the desire to take Palestine, and the countries of Syria, and he demandeth from you help in order to take Jerusalem. He hath chosen me and hath sent me to you because, being a Christian, my word will be believed by you."
Rabban bar Sauma, a Chinese Christian monk, recounts his conversation with
Catholic cardinals in Rome, c. 1290
-Based on your knowledge of world history, which of the following historical developments or processes facilitated the eastward spread of Christianity?

A) Silk Road trade routes
B) The Black Death
C) Zheng He's voyages
D) Japanese silver mining