Which of the Following Statements About the Mongols Is False

Which of the following statements about the Mongols is false?

A) Mongol men practiced unlimited polygyny.
B) Mongol custom prescribed that an heir marry all his late father's wives except his own mother.
C) Mongols had no written language until the tenth century, when they borrowed the Greek alphabet.
D) Mongol religion consisted of worship of a great god and spirits, as interpreted by shamans.
E) none of these choices