Questions Refer to the Following Passage

Questions refer to the following passage.
For these were a people who emerged from the confines of China, and attacked the cities of Turkestan, like Kashghar and Balasaghun, and thence advanced on the cities of Transoxiana . . . and of them one division then passed on into Khurasan, until they had made an end of taking possession, and destroying, and slaying, and plundering, and thence passing on to Ray, Hamadan and the Highlands, and the cities contained therein, even to the limits of Iraq, whence they marched on the towns of Adharbayjan and Arraniyya, destroying them and slaying most of their inhabitants, of whom none escaped save a small remnant . . . And thence they made their way to the lands of Qipchaq, who are the most numerous of the Turks, and slew all such as withstood them, while the survivors fled to the fords and mountain-tops, and abandoned their country, which these Tatars overran. All this they did in the briefest space of time, remaining only for so long as their march required and no more.
[T]hese Tatars conquered most of the habitable globe, and the best, the most flourishing and most populous part thereof, and that whereof the inhabitants were the most advanced in character and conduct, in about a year; nor did any country escape their devastations which did not fearfully expect them and dread their arrival.
The Mongol Conquest of Central Asia (1220-1221 CE) , Ibn al-Athir, historian
and biographer living in what is now modern Iraq
-Which statement best summarizes the claim or main idea in the author's account?

A) Mongol armies rapidly destroyed numerous advanced cities.
B) The people of Western Asia banded together to resist the Mongols.
C) When the Mongols attacked Khurasan, they ransomed the inhabitants.
D) No one knew why the Mongols suddenly decided to conquer Asia.